You can find the instructions in the "Model X Towing Instructions" PDF on your MyTesla Page. Here's the instructions:
If the car does not turn on, jump the 12V battery. This will provide enough power to access “Tow Mode”. There is no manual release for the parking brake. Jump Points are located in the front trunk.
1.Pull back the plastic cover located in the back of the front trunk compartment.
2.Carefully pull back the plastic cover of the fuse box which you will find to the far right. Use both hands as shown in the image below.
3.The positive terminal is located in front of the fuse box compartment.
4.The ground post is a bolt located on the passenger side of the compartment.
5.Attach your red positive lead to the positive terminal found in step 3. Attach your black negative lead to the ground post found in step 4.