First of all, to download the repository, you can run
git clone https://gitgud.io/Dav999/ved.git in a terminal wherever you want to put it (which allows you to pull in changes later without having to redownload everything) or you can download it as a zip/tarball with the download button on the right of the main repository page (next to "Find file"):

Any of those can be easily extracted on Ubuntu by double-clicking as far as I know.
When you have all the files (extracted), there should also be a folder called Source. If you first double-clicked the .love file, you should be able to run
love in a terminal followed by the path to the Source folder, like this:
love path/to/ved/Source