There are a couple of ways for you to get Office add-ins into your Office applications (Windows desktop version). If you have an Office 365 tenant, you can create a SharePoint app catalog and upload your manifest files to it: http://simonjager.com/office-add-ins-launch-in-office-online/
If you don’t already have one, you can get yourself an Office 365 developer tenant with the Office 365 Developer Program: http://dev.office.com/devprogram
You can also use a folder on your local drive as a manifest repository for your Office applications to look into for add-ins.
To get started, go ahead and create a folder somewhere on your machine. Now look at the properties (right click) of that folder and find the Sharing tab.
You need to grab the Network Path – this is what we will feed into the desired Office applications.
If you don’t have a Network Path set up right away (depending on where you create the folder) – click the Share button and go through the short wizard in order to configure it.
Now launch the Office application(s) that you want configure to use this folder (as an add-in catalog). Dig into the Options, head into the Trust Center tab and finally the Trusted Add-in Catalogs tab.
Enter the Network Path as the Catalog Url, and hit the Show in Menu checkbox.
Finally you need to restart the Office application in order for it to use the folder as an add-in catalog.
In the Insert tab – find the Store button and you will have a Shared Folder tab available. This is your add-in catalog which the Office application will look into for add-ins (manifest files).
All done – super easy!
Thanks @ for sharing!