right above the "Comment Box" you should see 4 names with download buttons (literally, they say "Download" on them)
Now, if you have a windows PC, select the 1st one and if you have a mac PC, select the second one (the last 2 are related to the gamejam)
the download should start automatically, once downloaded open the downloaded file in winrar and click on "Extract To", select where you want your new game to be in and boom, there you go, thats it