New Crew Member

To add somebody to the crew search for the person's name and select him/her from the drop down list. If you can't find the person in the list you can create him/her by selecting the last entry. Next, search for the person's job and select it from the drop down list. Finish by clicking Ok.
You can also assign a crew member to a season and inherit him/her to all episodes. This way you don't have to add the crew member to each episode. To do so, change to Doctor Who > Season 26 - Seventh Doctor (1989) and edit the crew there.