Sure, here are the steps to make a Spotify playlist collaborative:

1. Open the Spotify app on your desktop or mobile device and sign in to your account.

2. Navigate to the playlist you want to make collaborative.

3. Click or tap on the three dots (or the "..." icon) next to the playlist title.

4. From the drop-down menu, select 'Collaborative Playlist'. If you're using a mobile device, you might need to scroll down to find this option.

5. A small icon will appear next to your playlist title, indicating that it is now collaborative.

Remember, once a playlist is collaborative, all of its followers can add, delete, and reorder the tracks.