Since you're installing an app that has no native packages, it's not as easy as we'd all like it to be. The basic steps are listed here. After that, just extract Treeline somewhere and run (if it needs any more dependencies you're unsure of, report the error here and we'll see what else is required). If you want it to appear in the start menu, that'll require a bit more clicking (either putting it in the user menu or creating a .desktop file), but first get it to run, and then we'll talk about convenience