There is a gap between the block and the drive shaft pot joint O/S/F next to the bracket with the bearing in. You will see a 10mm bolt head and that's where the locking pin goes. Make sure you insert it right as it can sit just under the crank and that will not be the correct place for it. Also in the pin kit you get 3 pins so make sure you use the correct length pin.
My advice to you is if you have not done one before leave it alone and get someone who has because you could well kill a perfect engine.