Adding a chain link fence gate, to an existing fence.
Already has one post in the middle of the fence he could use.
But I think he has to make it an end post. It would be the hinge side.
He would have to add a tension bar, Tension Bands, Rail end into the tension band. On the latch side it would have a new post treated the same way. Does this seem correct

It may seem correct, but hard to say from the picture how an expert, or professional would go about installing a gate for you.