Crates are a great way to organize music you like on the site. To add a song to your crate, just click the Crates button on a track, which looks like a box.
When you click that button, a pop-up will appear where you can add the track to an existing crate or create a new one.
To access the crates you've made, click the same Crates icon at the top right of the page.
If you're looking to make a Crate on the app, you can find instructions here: https://help.digitaldjpool.com/en/articles/4132882-how-to-make-a-crate-on-the-app