You can, although it is well hidden!
Find your way to the User CP page, with the link mentioned by one of the posters above. The panel on the left, labeled VIEW, has three tabs under it: Messages, Profile, and Posts. Graphically, it is very easy to miss this, since the design of the tabs does not call them out very well.
The tab defaults to the first, Messages, and you'll see your Inbox, etc. Click on the Profile tab and then the Edit My Profile option under that to change things. (You'll have to supply your password to authenticate yourself again.) There are other items for changing Options, Contact Info, etc. as well.
I don't know why the User CP is not an option on every forum page, where Home | Help | ... are. Seems it should be. Seems that it should also be in the list of popup items at the lower right of each page, as well.