There are 2 ways to activate your Liferay DXP instance:
With an XML activation key that you request and receive from Liferay Support.
Online activation through Liferay Connected Services (LCS). Liferay DXP 7.0 introduced LCS as a way to activate Liferay DXP instances. LCS can also install fix packs, monitor each instance’s performance, and help administrators automatically manage Liferay DXP subscriptions. See the LCS documentation for instructions on activating your instances with LCS.