IPSec & NAT

Hi everyone!
I have a situation, and I hope this is the right place to ask the question! If not, please kick me repeatedly and shove to the right area.
I have an IPSec tunnel setup, my endpoint IP being 10.42.10.255. The remote endpoint IP is 10.42.10.254. I need to create a NAT rule, as the machine I need to access on the other end is 172.20.50.243. My local LAN subnet is 192.168.1.0/24. Where is in pfSense would I start to solve this issue?
Thanks,
Daryl 
How did you come up with the idea that you need the NAT?

With the right remote networks specified across the VPN tunnel, and firewall rules that pass the traffic, traffic will be routed fine. There is no need for NAT.

Well, it turns out the information originally provided to me was incorrect, and helps to answer why doktornotor questioned the validity of needing NAT! :)
Turns out my local IP will be 172.20.50.243.
There are 2 machines I am accessing on the other end, and they are 10.42.10.254 and 10.42.10.255. I need to NAT from 192.168.1.0/24 to 172.20.50.243, as the other end rejects the connection otherwise.Does any of this make sense?
Thanks,
Daryl