Well, not quite at the beginning but very near, I found lifting my arm out straight to my side, level with my shoulder, quite painful in the shoulder. With one position of my hand, particularly so. You may find, you cannot get your arm up that high to start with on one or more of the hand positions but it will come, it just takes time.
So this is an exercise that I persevered with until I could do it with no great effort. As weights can be quite expensive, I then used 2 milk cartons (2 litres each), as my weights, with half a kilogramme of water in each to start with. I slowly worked my way up to 2 kilogrammes in each, half a kilogramme at a time, as the strength in my arms and shoulders increased. The hand position that I found most difficult was with the back of the hand facing forward. I believe most people find this position the most challenging.
Anyway, see me on the video below and have a go. Bear in mind, you have to do this exercise regularly to see any improvement. I did it every day.