What is an A/B test?
An A/B test is running 2 variants to test against each other. In this case, you'll have your control which will be the original version of that section and your variant which will be the changed version of that section.
How to edit my variant?
In order to edit the variant, you will hover the section > click the beaker icon in the toolbar > click "variant" then you may begin editing once a blue bar appears below the label "variant" indicating you're now editing the variant version.
Running the A/B test...
You'll set up conversion goals, segmentation percentage, and results certainty by clicking the gear icon next to the label "Options/Start" which is to the right of the "Variant" and "Control" labels visible after clicking the beaker icon in the toolbar of that section.