IRC choose your own adventure.
step 1. pick a client.
I'm gonna start by looking at this list
and then ignore most of it because I'm only really gonna look at hexchat and kvirc I guess.
GUI desktop IRC clients
Hexchat
has builds for windows store, windows 64 and 32bit, flatpak, and also has a linux package in at least debian.
KVirc
has builds for... windows 64 and 32 bit, OS X, various linux packages, and FreeBSD
I did not find any obvious OTR functionality.
This client seems to be more into adding neat features compared to hexchat, like avatars.
mIRC
not open-source, but very popular because it has been around a long frickin' time.
web clients
these are harder to get setup, but easier for users to use. if you run an IRC server, consider setting up these for users.
thelounge
I haven't played much with this.
there doesn't seem to be an OTR plugin for thelounge.
kiwiirc
I have this installed, it won't persist a connection while you're afk like thelounge can.
doesn't seem to be an OTR plugin for kiwiirc :<
text-mode desktop IRC clients
only really two big ones as far as I care
irssi
usually included in linux and BSD package managers.
windows support is only through cygwin or WSL.
comes with OTR support compiled-in instead of needing a plugin.
weechat
also usually included in linux and BSD package managers.
appears to be no support for windows.
not to be confused with China's "wechat".
there seems to be weechat web GUIs available. only one I know of atm is:
step 2. find and connect to the IRC server
IRC servers can listen on whatever port they like and they'll be either plaintext or TLS (SSL).
port 6667 is usually the plaintext port and 6697 or 7000 being the TLS encrypted ports.
in almost all cases you will want to use the encrypted port. in the cases you don't, you'll know.
usually an 'irc' subdomain will be used, like:
irc.thebackupbox.net
right after opening your IRC client, you will need to either go through the process of adding the server to the server list, or, in some clients, you can just connect without any configuration using the /connect or /server command.
for...
step 3. join a channel
all clients I know of use "/join" to join channels.
example:
/join #default
once you are in, say hi, you may have to wait a decent amount of time before anyone notices and says hi back.
not everyone that is connected is currently at their computer.