It would probably be best to ask for Tanjunka support in the Tanjunka forums but otherwise…
Pick “Post->Services” from the menus. Pick “Add..”, Select “WordPress”. Enter a name for the service (like “My WordPress Blog”), Enter your username and password you usually use to log into WordPress. For the XML-RPC URL it should be wherever you have WordPress installed followed by xmlrpc.php. For example if your WordPress blog is installed at https://mysite.com/blog/ then the XML-RPC url should be “https://mysite.com/blog/xmlrpc.php”. Once you have that all entered, click “Update” under blogs. If it lists your blogs then it’s probably working. If not then one of those 3 things (username, password, XML-RPC is not correct)