http://wiki.abime.net/emulation/winuae/basics and you can find there link
http://guide.abime.net/gguides/winuaea.htm
If you received the following alert box:
"One of the following system ROMs is required:
- KS ROM v1.3 (A500,A1000,A2000) rev 34.5 (256k)
- KS ROM v1.3 (A3000) rev 34.5 (256k)
Check the System ROM Path in the Paths panel and click Rescan ROMs."
To manually select you ROM then:
a. Click OK
b. Go to ROM Properties and click ‘...’ button and set the path to your kick-start 1.3 ROM File.
Similar case is with WinFellow, but you need to go to Memory tab: