How to connect RM3 mini over internet to HA?

Configuration
1

I have two broadlink RM3 mini , one at home and one at my office.
My HA server is located in my home , and all the switches in my home are connected to my HA and my home RM3 mini is also configured with my HA .
My office switches are also connected to my home HA server using mqtt,

Now i m not able to configure and connect my RM3 mini connected in my office with my home HA .

Is that possible , how?

2

site-2-site VPN sound like the simplest method.

3

i havent used VPN before ,
is there any helpful hints how to set this VPN with HA for my broadlink rm3 mini ?

i am unable to understand how to use it .