Once you have figured out the winning variation, you have two options. One option is to Award the winning variation to rest of the users. This allows you to roll-out the variation to other users. To award a winning variation, click on Award test and select the winning variation and click Rollout.
The other option that you have is to close the test. Once you close the test, new devices will not be given the test. Existing users on the test will continue to remain on the test, until you run a new AB test. To close the test, click on close test button.