Welcome to the forums.
You say these files are sis files, thats correct, but are they for the correct Symbian platform?
Could you tell us the name of one of the files your trying to install?
Your best bet is to download sis files to your pc, then transfer them across to your phone via bluetooth, by either using a dongle, or built-in Bluetooth if your system has it.
Then when your phone receives the file, it will arrive like a text message, you then open it, and it installs in the correct area on the phone.
HTH
Micky
Check out these links, which should help, and keep you busy learning for a while..
http://www.n95users.com/forum/genera...new-users.html
N95 Tips