Head to over the latest release.
Download the jar file (currently cartjets-2.1.1-shaded.jar).
Drop the downloaded jar file into your Spigot plugins folder.
Stop your Spigot server and start it again.
With CartJets you can define entry points where custom minecarts spawn which can travel faster than normal ones to establish a custom rail network on your server.
To build the project you need at least a Java Development Kit (JDK) in version 11 and Maven 3 installed.
At first get a copy of the source code. Preferrably via git clone https://github.com/joestrhq/CartJets.git.
Initiate a build with mvn -Djarsigner.skip=true clean package.
The compiled plugin (cartjets-X.X.X-shaded.jar) will be available in the target folder.