Edit: this model needs a lot of tweaking before it can actually be printed. I recommend using this i'ble as a guide for your own model rather than trying to print this model.
Step 1: First Lets DO dimensions
Use the snap tool to snap the pieces into place. to make identical arms and legs you can either copy and paste after you make one or just make four solids with the same dimensions.
The body has:
arms and legs:
length and width 2.5
height, length and width are 5