Are you sure you have nmap installed?
If you are, then find out where it's located. You can try locate nmap or find / -name "nmap". The find command is guaranteed to find it if it's installed on your system, but will take a long time to finish. If either of those commands display any output that looks like an entry for nmap, then look at the path leading up to nmap. You need to make sure that directory is in your PATH environment variable, or you need to type the full path to run the command.
Fedora may have nmap installed in an "sbin" directory. That typically means it's intended for system admin-type accounts (like root). Normal users don't typically have any of the sbin directories in their path.