So, I've got two computers set up with the freelan binary, what is the easiest and fastest way to connect them now?

First you need to find out their public IP or - if they have - public hostname. Their address, so to speak.  You can use 
http://canyouseeme.org for that. One of the computers has to have UDP port 12000 exposed to the internet.  Then, if the 
first computer has $IP1 and port 12000 open you can connect the two as follows.  As root on computer 1: 'freelan 
--security.passphrase "my_secret"' and on computer 2: 'freelan --security.passphrase "my_secret" 
--tap_adapter.ipv4_address_prefix_length 9.0.0.2/24 --fscp.contact $IP1:12000'.  You should then be able to get a positive 
response from 'ping -c 3 9.0.0.1" on computer 2.