Try the documentation...

http://www.concrete5.org/documentation/installation/installing_conc...

If you're running it on your local computer, you'll need Apache, PHP and MySQL running. Try one of these...

WAMP for Windows -http://www.wampserver.com/en/
MAMP for Mac -http://www.mamp.info/

Firstly, you need to extract all files from the zipped install folder. Then use FTP to move the directory structure and all folders within to your public_html directory of your webserver.
Then make sure the config, files, and packages folders are editable by setting the permissions to 777 and recurse into subdirectories. Also, drill down into concrete/libraries/3rdparty and set the permissions of htmldiff.py to 755.
Then ensure that you have a DB created with a user assigned to that DB with all privileges. Visithttp://yourdomain.com and you will see the concrete5 install screen. Enter your database name, user, and password along with localhost as the root (most likely). Continue and concrete 5 should be setup and the admin account will be created with a password so that you can login and start editing/building.

And yes, this can be found in the documentation for C5, although I feel that "being writable by the world" isn't always understood by users who don't do a ton of dev work or permissions changes so I feel the permissions could be a little bit better explained.

The zipped download includes a file INSTALL that gives deatails on auto and manual procedures.