Just try again and again with different ladys and ask them directly how you can turn them so they can understand what you want.
In my opinion, there are 3 most important things: 1. you should know exactly what you want (or at least give this impression) so that your body leads too - its at least as important as your arms.
2. you should try not to lead too much - otherwise, the lady might loose her balance. You should only give the singnal for her to turn - and not turn her yourself. At the beginning, it might be difficult to get the balance between leading too less (the lady doesn't get the signal) and leading too much.
3. Talk with your partner and don't forget: dancing is fun! If you can manage, try not to use your head too much - listen to the music, feel the dance and just try until it works out - hopefully you can find a partner with whom you can do this.
Good luck,
Hine