can we add aim to the iphone

There is no AIM version that is compatible with the iPhone, and even if there was, installing it would require hacking/modifying your iPhone which is not supported by Apple, and could void your warranty.

There will be an AIM version for the iPhone and iPod Touch due to the iPhone/iPod Touch SDK released on March 6.

http://www.apple.com/quicktime/qtv/iphoneroadmap/

There are web apps available now that provide for this. JiveTalk is one.

http://www.beejive.com/

Also, Meebo is a very good online IM.
You sign in under whatever account, and start chatting

You can try using this link and adding it to your home screen. The only thing I don't like about it is that you must stay on it. If you open another webpage or close the screen it signs you out in 30 seconds. The link is

http://x.aim.com/ty/

That is most likely what will also happen under the SDK as well, since Apple is not permitting background activity per their licensing agreement for software developers for the iPhone (that is, you can't have an operation, such as staying connected to AIM, permitted while you are using another program on your iPhone)...so the usefullness of a program like that is a bit tenuous right now.