Question

How to running flow in modal dialog
I have a button and I wanna give action "flow in modal dialog" on my button but i don't know how to use the exist flow in my cases.
can I put the exist flow into the flow name in the "flow in modal dialog" ? because when I try to put the exist flow, the flow cannot to be find (Pega ask to make new flow in Data-Portal class).
Thank you before,