Hi Janine Herman. Currently, a user is only allowed to join one program at a time. But there is an option to save a video for later. To do this on the web, select the video that you would like to save. When the video appears, click on "Later" on the left side of the video. You will then be prompted if you would like to schedule a date for this video or simple "save for later". If you "save for later", you can find it under your "Watch Later" tab. If you are using the app, bring up the video that you would like to save and click on the clock symbol. You will only have the option to schedule this video for a particular date (and not "save for later").
There is not an option to bookmark a program. However, you can go the program's page and select the first video within the program. Using the above steps, you can save this particular video, and hopefully that will remind you of the program that you wish to join.
Let me know if you have any more questions.