Yes, you can.
Go to your dashboard - 1st page, click on an image, you will see the file's info.
Hover over the title or category or keywords - you see a pencil icon, click on that and then you change it.
In addition to Ricky's reply, in the case of keywords, when you make corrections, add, or change, click "Ok" then click "Save". Make sure you're at the image you intend to change before clicking save.
For the other changes, just click save when you make the change.