Log into Viggle as normal and follow the prompts to merge your accounts. Your Viggle and Perk Point balance will both be available to you.
You will be prompted in the app to create a Perk account and transfer your current Viggle balance. If you already have a Perk account, you will be prompted in the app to transfer your Viggle balance to your Perk account. If the email address you use for Perk is different than the one you use for Viggle, you will be able to update your account email to the one your prefer.