Plug-ins purchased in the SSL Web Storeare deposited directly into your iLok account.
When opening your DAW or inserting the plug-in for the first time, you will see an activation prompt. Press skip and sign into your iLok account.
Once signed in, the DAW will be able to successfully activate your plug-ins.
I purchased from a third-party (i.e. Sweetwater)
Plug-in licenses purchased through third-parties must be redeemed from an activation code. To redeem the activation code, open iLok License Manger and go to Licenses > Redeem Activation Code, follow the instructions and enter your activation code.
Once the activation code is redeemed you can proceed with activating your license.