building from a source, linux

[Cat Jordan]

Ok, please keep in mind I'm very bad at coding while reading this question.

I'm following the "building from a source" instructions on this page (http://opencolorio.org/installation.html). I made it to "run cmake..." before I got stuck. Here's what I got when i tried to put in the code as is.

"CMake Error: The source directory "/source/ocio" does not exist.
Specify --help for usage, or press the help button on the CMake GUI."

Using 'sudo' didn't help. when I added " .." o the end I  got this error;
"CMake Error: The source directory "/home/sigi/Downloads" does not appear to contain CMakeLists.txt."

I had navigated to the downloads folder at this point because that's where the file in question is.

Trying to move all these files to tmp/ociobuild didn't help either.

I don't know what I'm doing please help