During playback, under the Cameras section. In the center of the page under the "Settings" tab header you can select Optical Zoom. You can drag a box around the area you would like and increase the bar to zoom in the entire few. You may have to adjust focus in order to get the best clarity once zoomed.
Zoom level will need to be set during/after camera install as @MerakiJockey505 mentioned, once this is set the camera will start recording at the level of zoom selected. If you require to zoom on existing video you will need to export first and use your preffered video editing tool to zoom in the video.