Open-Realty add-ons can be found at the Open-Realty Extras site located at:
Add-ons may also be available from other publishers elsewhere on the internet, but the OR Extras site is a good place to look first.
Once you have located an add-on that you want to use in Open-Realty check to see if documentation for that add-on is provided. This should include instructions for installing the add-on.
If the add-on you want is located on the OR add-ons web site, then you can locate it, and install it directly through the OR Add-On Manager in the OR administration Control Panel.
Please see the Add-On Manager section in the Administration section of this documentation for full details on using the Add-On Manager to install/uninstall add-ons.
If the add-on is distributed as a compressed ZIP file then it can very likely be installed through the Add-On Manager assuming it and the folder contained therein is properly named.