How do I update Ubuntu manually?

I wanted to update Ubuntu manually, because I used CDMA USB modem and connected using wvdial, but it won't able to update Ubuntu via Update Manager, because my Ubuntu won't showing "Connected" message via network-manager.

Can I update Ubuntu manually? Am I should download separate files, or use terminal instead?

You can manually update via terminal by running:

sudo apt-get update
sudo apt-get upgrade

Additionally you can run:

sudo apt-get dist-upgrade

From the apt-get manpage:

dist-upgrade in addition to performing the function of upgrade, also intelligently handles changing dependencies with new versions of packages; apt-get has a "smart" conflict resolution system, and it will attempt to upgrade the most important packages at the expense of less important ones if necessary. The dist-upgrade command may therefore remove some packages.

Do this:

sudo apt-get update && sudo apt-get upgrade

in a terminal. Re-boot if it asks.

Hope this helps!!!