That tap goes into an existing valve body, so you will have 2 outlets off the same body if you install that tap.
Hence, the 2 handles.
If you want the existing tap to do a washing machine or dishwasher (20mm hose connection) - go buy a washing machine stop tap.
If you want it to connect to a tap (15mm connection ) - go buy a mini stop tap.
There is no descent way of connecting that tap to 1 outlet, unless you cap off one outlet