Because F = ma, if the acceleration is 0, then the forces are in equilibrium.
First, the man have weight(of course!), so there is a force pointing downwards labeled W(stands for weight).
And then, there is tension in the string, so there is a force pointing upwards labeled T(stands for tension).
Also, there is normal force, so there is another force pointing upwards labeled N(stands for normal force).
Finally, the normal force and tension balances the weight, so it should be in equilibrium.
P.S.: I am not specifically good at Physics, but I tried my best to help. If anyone sees mistake in my solution, please teach me. Thank you.