Ok here are the complete steps you need to do.
Download the forge mdk. Link is for 1.14.4
After it is finished downloading extract it to the folder you want to write your code it.
Once it is done extracting navigate to that folder in your terminal of your choosing. For ease on Windows you can right click open powershell here or in the file directory at the top just type cmd.
Once you have your terminal in that folder run the commands "gradlew genEclipseRuns" and "gradlew eclipse".
If they error give us the full error. If they say build complete or whatever you are ready to start programming your mod.
If you are still wanting to use notepad/text editor; you need your code to be under src/main/java/
Once you have your mod in a buildable state repeat step 3 but instead run "gradlew build" Your mod will be built and stored in build/libs/