To start, click Start Recording. Your screen will be recorded until you stop the recording. Once finished, you can trim the video before rendering the video as a gif for download.
Keep in mind there aren’t any optimizations made of the recording and it records the entire screen, which results in a very large image size if you record for a very long time. gifcap would be good for short examples and demonstrations. If you lower the resolution of your display (check your display settings) you will get a smaller graphic file.