Oxwall is an open source platform which includes tons of sites. Now i'm not saying it is not impossible to do what you want but this is not something that just "works" via-plugin often you need an API and after creating said API you can add it to platforms like add this or other sites can use your API to create the ability to share on your network. Often a feature like this is only possible if you have a lot of money to spend on it because you will find no quick set-up for this.