Make sure you added the custom dimensions to Google Analytics as described in the following article: https://help.datatrics.com/integrations/use-google-analytics-as-a-reporting-tool
One of the custom dimensions is called "Datatrics Group", which are filled with the following values:
For visitors in the A/B-test which are in the Datatrics group, the custom dimension "Datatrics Group" will be filled with the value show. For visitors in the control group, the custom dimension will be filled with the value hide.
To create segments in Google Analytics, head over to an overview where you can add segments (the audience overview for example). Click on the greyed out box "+ Add Segment". Next, click on the red "+NEW SEGMENT" button.
You need to segment on the following condition:
Datatrics Group | contains | show
Save it and you now created a segment containing all visitors in the Datatrics Group.
For the Control Group, create the same segment but change the value from show to hide.
You can use these segments in all Google Analytics views to see how both groups perform. For more information about how the A/B-test is set up, see: https://help.datatrics.com/en/articles/3392047-the-a-b-testing-methodology