In Apple Music, you can easily create playlists and combine music from your own collection with music from the ‌Apple Music‌ catalog. Here's how to do it.

Create a Playlist on iPhone and iPad

1. Launch the Music app on your iOS device and find a song that you want to start a playlist with.
2. Long press or 3D Touch on the song.
3. Choose Add to Playlist -> New Playlist.
4. Tap to give your playlist a name, a description, and a cover image if you want.
   
   
5. Tap Add Music, and then use the search field to find songs in your library or in the ‌Apple Music‌ catalog, or browse through songs in your collection below.
6. When you find a song that you want to include, tap the plus (+) button next to it. Note that you can do this for multiple songs.
   
7. Tap Done when you're finished adding songs.

Create a Playlist on Your Computer

1. Open iTunes on your computer and find a song that you want to start a playlist with.
2. Click the ellipsis button (the three dots) and choose Add to Playlist -> New Playlist.
   
   
3. Click the name to change the title, and click the placeholder cover image to add one. To add a description, click the blue ellipsis button and choose Add Description.
4. Add more songs to your playlist by browsing your library or the ‌Apple Music‌ catalog, or use the search field to find the song you want.
5. When you find a song that you want to add to the playlist, click the ellipsis button and choose Add to Playlist -> [Your New Playlist].

You can also import playlists from other people on iTunes by going to File > Library > Import Playlist.