Zipped: Go to http://tcl.sourceforge.net
and download the source. There should be some installation help on that site as well. TCL/TK is all one project, so you're only installing one thing.
Since you are "a total newbie" you might want to think about using one of the easier linux distributions, like Mandrake or RedHat. Mandrake specifically tends to be a good fit for beginners as well as seasoned veterans. The biggie benefit is they have package management systems, that allow you to easily install stuff like tcl/tk.