Focus 1.8 petrol 2008 no compression on cylinder 3

[Juddy]

Hi all newbie here so just wanted to introduce myself and also ask a few questions (sorry if they have already been asked)

2008 focus 1.8 petrol 130,000 miles, running/idling lumpy so did compression check and nothing whats so ever on cylinder 3,  all other's 1,2 and 4 good compression between 190 and 200 psi after 5 minutes had passed i noticed that the cylinder (3) had a little oil in it where as the other's hadn't which leads me to think it's not the rings as if this was the case surely it wouldn't sit there it would work it's way thru so my conclusion is it must be the valve/s. Anyway started stripping down and got to the point where i need to remove the timing chain but what is the best way to remove and obviously lock the crank etc. Also I'm by no means a mechanic but i dont mind having a go. Thanks in advance.