What you need:
Your blood 
Something to write with 
A paper 
Lit candle or lighter(fire) 
An envelope

When you write to Lucifer or any demon, write a formal letter. It could be dangerous if you do not. Scratch that this will still be dangerous.

Now as for the instructions. Simply write the letter in your blood on a piece of paper and seal it in an envelope. Then take the envelope and burn it.