How do I add this extra partition to my installed Ubuntu system?

1st option: See if you can use gparted to delete the 92 GB partition, given that nothing is in it. Then expand the Ubuntu partition into the empty space. Moving files in gparted can be risky for your ubuntu install, but if you haven't customized it out yet, then it should be no big risk because it does not take long to reinstall. You might not be able to do all of this from within Ubuntu. If that is the case you could just burn gparted to a disk and boot from that. Be very careful not to delete the wrong partition though.

2nd option: From Windows, delete both the extra partition and Ubuntu partition or merge the two. Then reinstall Ubuntu. Only this time select "Do something else." I believe it also says 'Advanced.' Then it will take you to a menu with the partitions. At that point you can select the correct partition (or create it) and format it to install there.

3rd option: You may want to use the 92 GB partition as a Data partition between Windows and Ubuntu. If that is the case, then you could just keep it and make it mount at startup. You would need to format it so Windows can access it (maybe NTFS). You would add this command to startup items in Ubuntu: /usr/bin/udisks --mount /dev/sda7 (Replace '7' with partition number.)

Through all of this just make sure you know which partition is which. I am not certain what these partitions are because I just see what Windows says (7.93 GB partition and 92.06 GB partition).

EDIT: This stands here only for educational purposes.

Ubuntu does not allow messing with mounted partitions, therefore you have three options:

1. (Preferred one) Use 91GB partition for your /home, ie, user files. This way, when you need to upgrade Ubuntu, this partition will not be touched, ie, you will not have to copy data from backup back to hard assuming everything went right.
   1. Boot into Ubuntu
   2. Open terminal by pressing ctr+alt+T
   3. Gain administrative rights by typing sudo -s; it will ask for your password; there will be no indication that you are typing it - just type and press Enter
   4. Type lsblk
   5. Find your 91GB partition; Check if it's mounted; if MOUNTPOINT column is empty, skip next step
   6. Unmount that partition by typing umount /dev/sda[number from the first column]
   7. Change mount point of 91GB partition
      • Get UUID for 91GB partition blkid; check for same /dev/sdaX as you used for umount
      • Backup before messing with system file: cp /etc/fstab /etc/fstab_backup
      • Type gedit /etc/fstab
      • There should be line starting with UUID=[UUID from blkid]; change column /something to /home
      • Save file
      • Only read following if there was no line with correct UUID
      • At the end of the file add line #mount home partition; # marks everything following it as a comment, so you can use whatever
      • Add another line UUID=[UUID from blkid] /home ext4 nodev,nosuid 0 2
      • Save file
   8. Reboot
   9. You should have 91GB for your home directory; check from file manager
2. Deleting 91GB partition and expanding main Ubuntu partition from live session
   1. Boot into Ubuntu live session
   2. Open Gparted by pressing super (Windows) key, typing gparted and pressing enter;
   3. Select your 91GB partition
   4. Press Delete
   5. Select your Ubuntu partition
   6. From menu bar Partition -> Resize/Move
   7. Triple check the operations that will be executed (they are shown at the bottom)
   8. Check if the operations are such: delete [91GB] partition; expand [Ubuntu] partition; Edit -> Clear all operations if not
   9. Apply changes by pressing ctrl+Enter
   10. Reboot into normal Ubuntu session
3. Deleting 91GB partition in Windows and expand Ubuntu partition. I am not sure to do this as windows does not understand ext4 formatting.

Check
http://www.howtogeek.com/howto/35807/how-to-harmonize-your-dual-boot-setup-for-windows-and-ubuntu/
and
http://www.howtogeek.com/116742/how-to-create-a-separate-home-partition-after-installing-ubuntu/
for reference.

Here is a good article on what has happened here with the partitioning.
https://www.centos.org/docs/5/html/5.1/Installation_Guide/s2-partitions-overview-extended-x86.html

If you are happy with having 85 GB free in your Ubuntu partition, then I would just leave it as is.

If you would like more space in your Ubuntu partition, then you would want to use a program like Defraggler to defragment Windows. You will want to use Defraggler because Windows puts some unmovable files at the end of its partition, and Defraggler will move them. Then you would be able to shrink Windows, sda2, to a smaller size. (Only do this from within Windows.) Then by using gparted you would expand sda3 into the empty space.