If you want to select which products will be displayed as recommended products, you have to set up your own collection. Go to Content > Pages > then to the tab Catalog and thet to the category you want to choose recommended products for, let´s say Meters. Then click on the pencil icon...

and choose the option Own collection

...then you will see the option set collection (2), so click on Set collection...

...now either select an existing collection and change it appropriately or create a new one...

In case you decided to create a new collection, use the + button to add the desired products. Done!