How to change my main computer in order to delete songs from my iPhone?

My main computer crashed and I want to be able to use my new computer as the main computer. At this point, I really don't care if everything on my iPhone is deleted. I have songs on it that I don't want on there anymore. If anyone knows how to do this please let me know.

You'll probably need to authorize iTunes on the new computer before you can sync your iPhone with it. In iTunes go to Store > Authorize This Computer and it should walk through the process.

NOTE: This can only be done 5 times, so if you're at your limit you may need to visit Apple's website to "reset" the authorizations.

If your trying to manuely do it you have to click on the iPhone tab on iTunes and where it shows your iPhone picture look down and there should be check marks and the last check mark should say "Manually Add/Delete Music " and check it and go to your music on your iPhone and look for the ones you need to delete and your good to go