You need to add it in the "outside_access_in" acl.
It is simpler to work from the command line and enter these commands:
static (inside,outside) udp interface 69 10.20.30.46 69 netmask 255.255.255.255
access-list outside_access_in permit udp host <ip of 3825> interface outside eq 69
I am 100% certain of this config. I am also 100% certain that it will not affect any current users when you apply it.