First you should wait until your return is processed and you receive your refund if applicable. Then log into TurboTax and you will see an option to amend your return on your home page. Follow the instructions to amend your tax return. You need to go back through your state return and find the option that indicated you were a fisherman or farmer and change it.
I'm not sure it will affect your tax though, as the special rules for fisherman and farmers in Virginia have to do with paying in estimated taxes, so it may not affect your income tax. If you see your tax does not change when you remove the designation, then you don't need to file the amended return.