My pothos sits on the bottom of the cage. I run the vines up and around the vines and mildew resistant rope I use in the cage. I attach with wire or small zip ties to the screen of the viv
Get the hanging pots if you didn't already buy the pothos in one. It has a hanger on it. Just zip tie the top of the screen to the hanger. This will allow the pothos to grow off the side of the pot and down into the cage. I would also recommend a 6500k grow bulb to really let it grow.
I just got a sturdy plastic planter with drainage and gorilla glued a couple really strong magnets to it, got them at Lowes for $2.50. It's easy to move for cleaning and setup.
My hanging pothos are big and heavy so attaching to the screen would result in catastrophe. I put a support beam across one side of the top of my cage and zip tie the plant to that. I originally had them tied to it by rope and over time the rope frayed and broke so I learned that I must use something less likely to degrade.