Mounted drive needs to be double-clicked at least once before other applications can use it

What you describe is normal behavior for partitions on internal drives. Internal partitions by default are not automatically mounted if they are not automounted through the configuration file /etc/fstab. Such partitions are shown in the left panel of Files, and you can click these icons to mount the partition before use.

If you did not take special action, then indeed you do not have automounted that partition. You can automount by manually editing the configuration file /etc/fstab, although you can also use the utility "Disks" (installed in a default Ubuntu system) to configure the drive for automount during startup.

In Disks, click the partition. Then click the "gear" icon and select "Edit mount options". In the "Mount Options" dialog, select "Mount at system startup" to have the partition automount.

On a related side note: make sure Windows Fast Startup is disabled, and that the Windows system is fully shutdown before you use the partition in Ubuntu. Otherwise, the partition may not be properly closed, and that will give problems mounting and using it in Ubuntu.