I am trying to start my running pothos plant with a stick in the pot with so many fails - yellowing, root rotting, or just not growing.
How to Start a Climbing Vine Plant
Certified GKH Gardening Expert
From experience it can be difficult to train or keep a Pothos growing upright onto a trellis.
They just tend to be happier trailing down.
If you still want to try to train it upright. I would use a trellis and you can attach the plant using plant ties.
Plant ties that are soft and can be twisted around the plant stems without harming the stems can be purchased at most garden centers.
Here is a link with care requirements of Pothos.