How to put song ringtones on your iphone4?

Hi, i want to download a song off of itunes and put it on my iphone 4. But, i downloaded 2 songs previously, and tried to put them as my ringtone, but it wouldn't let me. I did what i was suposed to, i was to options, then clicked "get info" or something, just like what somebody (many people, actually) told me. But when i click "get info", when i try to change it, it won't let me.

To put songs as your ringtone, you have to buy them at the ringtones section (when you scroll down on the musician page and you click on it) but you have to pay the same price as the regular songs on the iTunes

Use iTools its easly set your songs as Ringtone