How do I tie down a backpack to this bike rack?

I recently bought this this e-bike for my daily commute and would like to strap my backpack down to the bike rack that it came with. I bought some bungee cords but I'm not seeing any loopholes on the rack to latch the hooks onto.

Does anyone have any advice on how to make this work?

In my first attempt, I hooked them onto the diagonal bars on the left but that ended up pushing my backpack too close to the bike seat which cause my heels to make contact as I pedal. The hooks slide around and have no tension everywhere else I try to hook onto.

The bike is a Triban E Fold 100 (if helpful)