If you are using Windows 10, just follow the instructions in this video.
If you aren't comfortable doing this and would rather have me do it - that's fine, but you must send me an email right away saying so.
If you edit the Windows path variable yourself, be very careful that you don't delete any data that is already there (which would mess with other programs). Here are text instructions for any version of Windows: http://www.java.com/en/download/help/path.xml
For Windows 8 and earlier: If you are editing an existing path environment variable, then you need to add a ; at the end followed by the path to your Java bin folder, which would be C:\Program Files\Java\jdk-14.0.2\bin or something similar.
For Windows 10: Once you go in to edit the path environment variable, you will see a list of folder locations and you can select new to add a new one, which would be C:\Program Files\Java\jdk-14.0.2\bin or something similar.
After changing the path variable, restart Textpad and then you can go back and re-attempt step 7 of "Installing Textpad in Windows".