Be sure to keep in mind that you'll be limited to cutting your rope light into discrete measurements. You can only cut rope light between "cut marks" or you'll break the electrical circuit of the lights. Each of our spools have either an 18 or 36 inch distance between cut marks and can vary per spool. Be sure to check the specification for the color you are interested.
Make your cuts in the rope light with a very sharp cutting instrument so that you don't significantly compress the rope light. Line up the pins and holes in your accessories and insert the sharp ends of the pins into the cut end of the rope. You'll need to use a firm hand in installation to make sure you make a good connection between the accessories and the rope light internal wiring.
Using adapters to branch off in different directions whether you are using a Y or a T, you can avoid the need to run extra extension cords. We have both short T's and Y's with longer extension arms to allow you more flexibility in your project layout.