Serato DJ 2.5.0 and above activates your Expansion pack licences automatically upon login.
Steps on how to sign in and activate your expansion packs can be found here - Activate Serato DJ Pro or Expansion pack
If you are using Serato DJ Pro version 2.4.6 or below, the activation steps are slightly different. Information on how to activate your expansion packs on version 2.4.6 or below can be found here - Managing your licenses in Serato DJ Pro 2.4.6 or older
If you have any issues activating...
If you are having any issues activating products inside Serato DJ Pro, contact the Serato Support team by opening a help request here.