Adding a Web Map Service (WMS) in QGIS using a URL.

Click Layer > Add Layer > Add WMS/WMTS Layer.., or click the icon.

Click New

Give the connection a name and enter the URL to the WMS map server.

Click Connect and select the WMS you want to add.

Choose PNG as Image encoding.

The WMS will load with its default coordinate system. Change if you want by clicking Change…

Click Add and Close to add the WMS to your map.

The WMS will display on your map.

Read more about adding a WMS using a connection file.