You can set up your review cycles by visiting Manage Account > Review Cycles. Alternatively, you can set up your review cycles 'on-the-fly'
To create a new cycle, press the "+Add" button in the top-right.
*Note: Start and end date are merely reference points for the reviewer. For example, in the screenshot above, you will notice that we are doing 2020 Q2 reviews. I have established April 1st-June 30th as the reference start/end dates. The reviewer will see these at the top of the form when they go to fill out their review.
You will also notice there is a checkbox for Goals. If you are using the goals module, it is likely that there may be certain review cycles that you may not want employees to use. Be sure to uncheck those boxes. For more information on goals/review cycles, refer to Evaluate an employee's goal progress.
For more information about Review Cycles, please refer to Understanding review cycles.