How to get music on my iPhone from iTunes?

I've been dealing with this for a while, and I'm not new at this- but I just got a new computer, and I synced my iPhone for the first time and I downloaded all my music. But when I click and drag a song from my computer to the section for the songs, the box doesn't highlight in blue, it stays gray and I can't put them on my phone. I've looked up why this is happening, and I went into the settings and clicked the box to manually put them in, but then it asks me if I want to clear my whole library. And that is a big no-no. Someone please please help!

It sounds like the music isn't really there, only a shadow, which is why it is gray not blue.

Go onto the store. Go to purchases. Download your previous purchases to your new computer.

Then you can access and sync the music.