Assemble the left side of the arm as in this photo. The top left screw in this photo should be 10mm and only screwed through until the screw end is flush with the edge of the perspex. The top right screw should also be 10mm and the bottom right 8mm:

Attach it to the central piece with a 10mm screw:

Slot a servo with a single horn into the square slot and hook it in place with two of the servo clamps.

Once it is in place you can wind the cable around the clamps and clip it on to the header pins

Slot the central brace into the main strut as shown in the photo and tighten up the screw to hold it in place

Assemble the right hand side of the arm like so:

Slot the piece you just assembled on to the other side of the central brace you just attached:

Put the servo in place and clamp it on like you did on the other side:

Then wind the cable round and clip it on:

And finally put an elastic band around the base to hold the clamps in place:

You can now put this part to one side until you have built the grip.

Take the last servo (with a single horn) and slot the small piece shown on to the end of the servo furthest away from the horns

Then slot the two supports on to the two pegs sticking out of the small piece you just added:

Then add the base; first slot it in place like in this photo:

Then rotate it down so it sits flat against the other pieces: