Add your teams workspace using the /server command.
/server add slack myteam.irc.slack.com
Next you need to turn on ssl using the /set command.
/set irc.server.slack.ssl on
After this, all you need to do is set your nick and your password.
To set your nick use the /set command.
/set irc.server.slack.nicks "mynick"
To set your password you need to go to https://my.slack.com/account/gateways. Once you've found your password, enter it using the /set command:
/set irc.server.slack.password mypassword
After all this, just connect using:
/connect slack
and you're all done!