I want to include an external Photo drive in my current Time Machine backup. How?

I just set up my Time Machine last night. I have two additional external hard drives attached to my iMac, one with photos, one with music. I wanted those two external hard drives to be included in my Time Machine backup, but apparently I did something wrong in setting up Time Machine because it appears they have been excluded from the backup process.

I see them listed in the exclude list, but I see no way to add them to Time Machine backup. The whole reason I wanted to get this backup set up was to make sure my photos and music were coppied to the backup. Is there a way to add these two external hard drives to my Time Machine backup now that it has been set up? If not, is there a way to start over and re-setup the Time Machine so I can include them?

It seems like it shouldn't be so complicated. What am I missing?

Thank you for your responses.