Set up a simple repository using a web server with its default configuration. The key is the directory structure. The documentation does not mention it explicitly, but it is the same structure as a local repository.
To set up an internal repository just requires that you have a place to put it, and then start copying required artifacts there using the same layout as in a remote repository such as repo.maven.apache.org. Source
Add a file to your repository like this:
mvn install:install-file \
-Dfile=YOUR_JAR.jar -DgroupId=YOUR_GROUP_ID
-DartifactId=YOUR_ARTIFACT_ID -Dversion=YOUR_VERSION \
-Dpackaging=jar \
-DlocalRepositoryPath=/var/www/html/mavenRepository
If your domain is example.com and the root directory of the web server is located at /var/www/html/, then maven can find “YOUR_JAR.jar” if configured with <url>http://example.com/mavenRepository</url>.