In this video I show the most common 7th chord shapes, it’s all pretty self explanatory! for the theory you can also checkout these other lessons:
https://www.giannichiarello.com/understanding-how-triads-and-other-chords-are-built
https://www.giannichiarello.com/from-the-major-scale-to-the-harmonized-scale-pt-2-7th-chords
And the shapes I use are here:
hhttps://www.giannichiarello.com/LESSON%20MATERIAL/7th%20chords.jpg