Old tech, new router. Need simple list

I am overwhelmed. This product, RB951G-2HnD, is more than I want but exactly what I need. I just need simple instructions on how to establish a VPN between 2 of these models. They will be setup as client computers_A:->MikroTik:->ISP_Cable/DSL box:->Internet = Internet<-:ISP_Cable/DSL box<:-MikroTik<-:client computers_B
I have looked on the web and searched this forum and found many instances using VPN server. Does one Mtik need to be a server in this instance? or both? I’ve done enough IT to be dangerous without using IP/Routes/Tables etc. every day or week, so I don’t know that stuff. I can follow pictures or instructions if they’re clear but most assume that you already know a whole lot and I’m stupid on network stuff.
Any help appreciated, thx.
TxTom

Are the Cable/DSL services providing static IPs … or dynamic IPs?

My final answer is ‘dynamic’. Although experience tells me that the cable modem provider binds the IP to the cable modem to manage their network easier, it could change. The DSL isn’t paid for static IP so yes, that definately could change more than the cable modem when rebooted/power outage. At one end is a DSL modem, the other is a cable modem.
I have configured one for VPN server and can log into it from outside that network, which is fine. However we don’t want to login to VPN from all clients, we would like just to make the complete internal network use all VPN because it has connectivity through the far end for all our needs. Hence settting up the VPN between 2 offices and having office B access everything through A’s VPN (is that clear?)
Thanks