So you haven’t got any way of getting water to your back yard other than using a tap?
Here’s a set up that can enable you to get two stations of retic functioning well. Start by removing the garden tap and then screw a 15ml brass T piece into the outlet. Then use a 15-20ml nipple in the tee to connect the ball valve, which will allow you to isolate this retic if you ever need to.
From the ball valve you will need a 20-20ml nipple to allow connection of the digital controller. This one is a Rainmaster and is simple to use and easy to program, but they all do pretty much the same job.
From the controller you can either run one line of retic or (as in the picture) you can add an alternating valve to create two separate stations. Be aware that these valves only allow water flow of 20l/min and do require a minimum pressure to function. If this minimum pressure isn’t there they may not switch between stations.
When setting it up test it at each stage for leaks and be sure to use threadseal tape to minimise the possibility of this. And then when programming the controller be sure to schedule two start times if you have an alternating valve.