1. Get on a computer with iTunes or whatever you use
2. Open a tab with YouTube
3. Open another tab with a MP3 converter (to get the songs into MP3 format)
4. Find a song (lyric videos work best)
5. Copy link
6. Put the link into the converter
7. Get the song into a folder (just a normal one on the computer)

Get all of the songs you want before continuing (into the folder)

1. Open iTunes
2. Plug device you want the songs on into the computer
3. Click onto your phone through the computer screen.

It should display songs/usage/remaining space

4. Select the songs in the folder
5. Drag it into the "my phone" section, or "Music"
6. Wait until it's downloaded

It's legal :3 go crazy!!

Also

Whatever you name the song in the folder is what it will be named in your phone. DO NOT HIT A RANDOM KEY UNLESS YOU WANT THE MOST DEPRESSING SONG ON YOUR PLAYLIST NAMED "r"