# First open irssi from terminal:
irssi

# From there, connect to the libera chat server:

/connect irc.us.libera.chat

# And reidentify as your username

/nick <username>

# And register with nickserv if you haven't already,

/msg NickServ REGISTER YourPassword youremail@example.com

# Otherwise simply identify NickServ of your name/password

/msg NickServ IDENTIFY z3rOR0ne YourPassword

# Finally join the channel you wish to partake in:

/join #channel