How to use VirtualBox's DHCP server for a pfSense guest machine so that other guest machine's within the internal network can connect to it

[trickortreat]

Clarification:
My goal is to have pfSense set up using VirtualBox's DHCP server. This is so that it could be connected to the other guest machines on the internal network. Currently, all my other guest machines (not including pfSense) are connected to each other on an internal network within VirtualBox.

My goal is to take the guest machines and make pfSense their default gateway so they have internet access through pfSense.

The problem is that pfSense already assigned the LAN interface with its own IP from the DHCP server. I want it so that the LAN interface is assigned an IP from VirtualBox's DHCP server. Also, for my own reasons, this all has to be down through the shell on pfSense.

I have already disabled DHCP using pfSsh.php playback disabledhcpd, but don't know how to assign the LAN interface the IP from my own DHCP server.

Within pfSense, I am only able to assign static IPs.

How do I assign the LAN interface an IP from VirtualBox's DHCP server so that it is part of the internal network?