First, find out which section your man page belongs to. If its a command, it probably belongs to section 1. You can read the manpage for the man command to see a description of the different sections and their corresponding numbers.
Copy your man page to /usr/local/share/man/man1/ (change 1 to your section number if need be). You can also install it to /usr/share/man/man1/, but it's best practise to use the local directory for files that are installed without using the APT package manager: