I see you have some great help - just going to wish you well.
The link jrob gave you is very, very good. That's how I learned to do it and never have a problem. Just take your time, print out your templates, and mark. Practice on something and you'll have the hang it in no time. Carol
Print out the different sections of the design and measure, measure, measure. There are different types of marking pens that disappear either with air or water and they are very useful. Painters tape does a good job of holding all the pieced together. Draw you hash lines (cross x's) and I like to start with the section in the middle.
There are several tutorials on split designs...here's one.