Tensioner pin has to be pushed thru and re-loaded from the front.
It is a ratchet design and holds it's last position, which will be too tight for a new chain.
Failure to do this will result in much engine damage. [ breaks camshafts right in half ]
Very common/costly over-sight. Even by good mechanics.

Tutorial Note for readers:

The concept of the ratchet design of the extending pin was to overcome a problem with earlier style tensioners loosing their pressure from sitting. The results of those was the famous "Chain Rattle " of earlier engines. The chain
would be loose fromthe tensioner relaxing until the engine got the oil pressure back up for the tensioner to do it's job. So, by having a ratchet type tensioner , the pin can only extend longer , [as the chain wears/lengthens], but the ratchet never lets it shorten, regardless of how long it sits..It holds/locks it's last position .
This eliminates the possibility of a loose tensioner at start-up, but if one does not know this when doing any chain work, they put the tensioner back in and it is too tight b/c of it's last extended/locked position..thereby having the probability of serious breakage damage to valve-train parts.

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A Dalton