How to add a new WMS connection in QGIS

In the QGIS browser window right click on WMS/WMTS to add a New Connection:

In the window give the connection you are adding a name and if adding a WMS connection copy in the URL you were sent ending in apgb.wmsx

The WMS connection will appear in the Browser under the name chosen in the previous window. Expand to reveal all the available layers and choose the ones you would like to view by right click and 'Add Layer to Project'