To install extensions manually, download the required extension from razor archives.
1) You can use the auto-installer located in the extensions area of the admin dash overlay.
2) Prefer the manual method, this really is this simple too...
Download, Unpack, Upload, Configure...
Download the file from the website. Unpack the file to your computer. Upload the extension to your webserver location where razorCMS is running. Log in and click the admin overlay icon, access extensions are and set any settings required.
To use the extensions, simply go to the page you wish to use the extension on, click the edit button and use the puzzle piece icon to add an extension in the location you wish.