|You have at least two separate issues here so let's take them one at a time in order of importance.|
1) Establishing your point-to-point wireless connection between physical locations and ensuring you have network connectivity between them.
2) Configuring clients at remote location.
If you don't know how to do #1 yourself you will need to contract a professional to do it for you. I have done it, several times with enterprise level equipment, but I can't type up a step-by-step guide for you that will work as how it's done is dependant on the equipment you use and it's capabilities.
As for #2, once you have established network connectivity between locations you have two choices. You can either put a DC in the remote location (recommended) or you can have the clients authenticate across the WAN link to the DC in the main office (not recommended).
If you opt for the second choice and decide to make clients authenticate across the WAN link unless you have over 200 devices/clients using IP addresses, you could have them all in one subnet and then the remote clients would setup exactly the same as the clients in the main office. Because your wireless WAN link will be setup like an encrypted VPN tunnel, the actual network itself behaves (logically) like one, unseparated unit. Like going from one room to another or from one floor to another within a single building.
The recommended method would be to put a DC in the remote location that is synchronised with the DC in the main office. Then all remote clients would authenticate to it and keep that authentication traffic off of the WAN link leaving more bandwidth for them to work with.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.