There’s really no install required on Ubuntu. Just extract the downloaded folder and put it somewhere on your hard drive. I keep mine in ~/apps/julia-0.6
You then just have to make sure the Julia executable (inside the bin folder) is available to your shell. You can add that bin folder to your PATH environment variable, or create a symlink from /usr/local/bin/julia to the bin/julia in the downloaded folder. I prefer the second option.