I don't know what category this should go into, but I'm gonna stick it into "General".

I noticed a lot of users have little personal items on the right side under their username. How do you get those?

I think you mean the left side.
Those images are called avatars. First you need to choose a suitable image & upload it to the server. Make sure it's a reasonable size & in JPEG or GIF format. http://www.simviation.com/yabbupload.html

Then click the Profile link at the top of the forum page. Scroll down to where it says "I have my own pic:" & check the option. Add the full path to your image in the box. It will look something like this. http://www.simviation.com/yabbuploads/myavatar.jpg

Then click Change Profile.