Step 1: Tie The First Knot
(Sorry the picture is kind of blurry)
Step 2: Thread The Paracord Through The Knot
Step 3: Weaving
Step 4: Tying The Final Knot
Note: You also might want to add a little bit of glue to the knots so they don't come undone
Also you can make different colored key chains for different keys and make yourself even more organized and make life easier.