How do I select multiple candidates at once to change their interview status?

To select scattered candidates (i.e. candidates that are not grouped together), press on the CTRL key and select the desired candidates. This method will allow you to only select the candidates you click on.

To select a large group of candidates, click on one candidate. Then, press on the SHIFT key and select the last candidate in the group you wish to select. This will allow you to select all the candidates between the first and last one you clicked on.