how do i synk my iphone to another computer

You can't. iTunes is set up to prevent file sharing so if you try to sync your phone to a second computer it will erase everything on your phone.

For syncing what?

If for any iTunes content - music, tones, movies, tv shows, or apps, you can't without all existing iTunes content on your iPhone being erased first. The same applies to any photos transferred from your computer to the iPhone via the iTunes sync/transfer process.

I used TouchCopy to transfer my iPhone to my new computer as recommended here

https://discussions.apple.com/docs/DOC-3141