Where do I find steel for the fishing rod? Thanks for any help.

First, befriend outlaws a bit. After that explore the forest until you encounter an unreliable outlaw that talks about raiding a trading cart in the fields. Do what he says, then share the profit with him and he'll tell you that you can mine it in the caves near the meadow. After you try mining some, talk to Rohan and he'll tell you how to make some steel.

Or you can just buy them from the blacksmith

OR talk to Myaun and buy the fishing rod from him.