Minimum: Just watch and absorb what you can. Or not. If you don't see 7th chords in the music you already play, or you just want to tackle them later, then you can skip this section.
Ambitious: Be able to recite the notes in each type of 7th chord given a random root, as we already did with triads. Memorize all 15 7th chord shapes. Be able to identify the 1 (root), 3 (or b3), 5, and 7 (or b7) in each shape. You don't need to be fast at this yet. Just make sure you've got all the information from the attached PDF in your brain, even if it's slow to access.