Minecraft Forge problem?

I wanted to install Forge for 1.12.2 but when I download it only a .jar file comes with which I can't do anything except open it in any text program. Does anyone know what I can do?

First of all: Did you choose the right Forge site files.minecraftforge.net

Then:

Right click on the file, open with and then select Java

If that doesn't work, drag the file into an empty folder, Shift, right-click an empty space in the folder. Then open it with PowerShell / Command Center. In this window you then enter: java -jar name of the file.jar

If both of these are not possible you have to install Java first.

https://www.java.com/...manual.jsp