How to ssh to another computer using ngrok or similar tools? Basically, using a domain instead of local ip

I'm trying to ssh to my guest machine running Slackware 14.2. I'm able to do it using the local ip but how do I do it with a domain? My host os is Debian 10

uname -a of Slackware
Code:Linux sandalphon 4.4.14 #2 SMP Fri Jun 24 13:38:27 CDT 2016 x86_64 Intel(R) Core(TM) i5-2430M CPU @ 2.40GHz GenuineIntel GNU/Linuxuname -a of Debian
Code:Linux sandalphon 4.19.0-6-amd64 #1 SMP Debian 4.19.67-2+deb10u1 (2019-09-20) x86_64 GNU/Linux