KV9200 Issues

[Alex KL-1]

Yes, you can connect one end to F1.
From your link, it seems to be a 2k pot. Too low value; will load too much the 530V supply.
You can choose a pot >1M ohm, since the focus grid almost don't drain current.
In fact, I use a 12M pot I found in a local electronic store when optimizing focus.