At the moment Skype is unavailable for Symbian Belle. For further information on this, please get in touch with Skype themselves as they will be the ones who can provide you with more details.
Feel free to post any other questions you may have.
There are a couple of threads dealing with Skype for Belle:
Basically you have to download Skype_2.1.23signed.sis, copy it to your phone, and install it manually.