Hi Len and Welcome to Ninjette!!!
Finding leak is easy:
1. clean off all signs and smears of leak, if you have to take off bodywork leave it off
2. warm up bike and go for short ride
3. come back and leave bike running
4. go look at exhaust pipe and see what's dripping and where. Might help to hold pieces of paper over exhaust to catch leaks and make droplets more visible. Follow drops upwards to find leak.
Fixing leak, may be more difficult.