Note: download url is the at the end of this article
Upload the plugin to the Plugins directory of NopCommerce (in hosting0 and Go to Configuration -> Plugins and Ensure that you have installed (by clicking on install button) the plugin.
After successfull installation, you will see a new System Role called "WebService Manager".
Goto Configuration -> Access Control List and verify that "WebService Manager" role has the four permissions;
Now, go to Customers -> Customers grid and edit any or admin customer (that you want to give permissions to these api resources) and click on edit and make sure that the customer is added to the "WebService Manager" role (if not then add it).
Now you are good to go. Open up broswer and type http://localhost/api/default (the base url i.e http://localhost maybe changed in your case) and there you have it.
In order to test versionning type http://localhost/api/v1/default and http://localhost/api/v2/default and you will see the following result.
And there you have it. If you have any concern regard to the template plugin, please comment and i will try to reach and help you.
Source Files + Plugin