Ok, so you have space to mount servos. If there are no holes you can make them using a small drill (about 1.5mm) - it's just to mark where screws will be. Mount servos using screws (which you should find in servo bag) to the servo holder. The last step is to connect pushrod...
Then we have a U shaped bracket and here we need attach two round horns for connecting the two servos for the head. Again before securing the bracket to the roll servo we need to make sure that the position of the servo is in the middle so it can rotates 90 degrees in both direction...