Install Java Runtime Environment (JRE) or Java Development Kit (JDK)
Open a terminal or command prompt
Navigate to the folder containing the .jar file
Run `java -jar filename.jar`
Replace `filename.jar` with the actual file name
On Windows, you can also double-click the .jar file if file associations are set
If double-clicking does not work, use the command line method
If needed, make the .jar file executable on Linux or macOS with `chmod +x filename.jar`
If the .jar requires a specific Java version, install that version first
If the .jar does not start, check for missing dependencies or errors in the terminal