The HoloLens understands several gestures.
To select an object, try using an air tap. Use a hand ray from your palm to target the item. You don't need to raise your entire arm, you can keep your elbow low and comfortable. Point your index finger straight up toward the ceiling. To perform the air tap gesture, pinch your thumb and index finger together and then quickly release them.
If you are using a HoloLens 2, you can also use a poke gesture to select.