Unable do add pgsql-arraymath extension to postgres database

I'm trying to add pgsql-arraymath extension to a postgres database however I can't succeed. Source code is avaialble here: https://github.com/pramsey/pgsql-arraymath. What I tried to do was to unpack the files and copy c, control and sql files into postgres extension directory and after that run CREATE EXTENSION query however it doesn't work. Should I compile something? If so - how? BR