Hi cvluster, welcome to the forum
I found it easier to put the domes on one at a time. All you have to do is hold the dome on the breast with one hand and pump with the other. And pinch the tubing on the free dome so you get suction. Once the first dome is on good and tight pinch the tubing on that dome and put on the second dome and pump. It's kind of a juggling act but that was the only way I was able to get the domes on myself lol
Much luv and happy pumping