You have to run the following command in the terminal:

mvn install:install-file -Dfile=<path-to-file> -DgroupId=<group-id> \
-DartifactId=<artifact-id> -Dversion=<version> -Dpackaging=<packaging>

where:

path-to-file: is the path to the jar you want to install in the local repository

group-id: the group in the maven repository you want to use

artifact-id: the name that the jar will receive when you want to use it in a pom.xml

version: the version of the jar/library

packaging: the type of package it is, usually is a jar