[Arraminta]

The easiest way (might be a bit smelly for a while) is a Cath face says.. Identify where she wee's... Put the wet wee soaked substrate into the potty and then put it where she is wee-ing! Once she has got used to the potty you can start gradually to move it where you want it to be.. Step by step keeping wet wee soaked sawdust (just enough to smell) in the potty and thoroughly cleaning where the wee is in the cage...
Patience will pay off.. My old hammy Tillifer would always wee in her bed, on her wheel in her tubes.. But I even managed to potty train her Lols.

Good luck
Arraminta x