I thought I registerd to have a username and password for isketch but when i type in my username it doesn't let me put in the whole thing. How do I do that.?

Registrations aren't readily available yet.

2.0 is right, registrations aren't publicly available as yet.

...when i type in my username it doesn't let me put in the whole thing. How do I do that.?

iSketch will only allow a maximum of 12 characters and as I imagine your chosen username is the same as your 13 character screen name here, this may be why you can't enter your entire name :)