Choose Tools → New BBS Session…, pick Telnet (or RLogin, SSH or raw TCP) and enter the BBS address. The session gets the BBS settings:
For sessions you already have, right-click them (or their folder) and choose Apply BBS Settings…, or use Options → Apply BBS Settings to This Session…. Turn on iCE colours under Session Options → Terminal for art that uses bright backgrounds.
Saltbush answers the BBS's cursor-position question, so BBSes that check for ANSI find it.
RLogin logs straight in. Most BBSes read the RLogin “client user name” as your password, so keep it in a credential: Tools → Credentials… stores the user name in the settings and the password in the desktop password store (KDE Wallet or GNOME Keyring through secret-tool on Linux, Credential Manager on Windows). Then choose the credential on the session's RLogin page.
Downloads start by themselves when the BBS sends a file, into the session's download folder (File Transfer page). When a download already exists Saltbush renames, overwrites or skips it, as you choose.
Uploads start when the BBS is ready to receive: start the upload on the BBS and Saltbush asks which files to send. Transfer → Upload with Zmodem… also works: the files are sent as soon as the BBS (or rz in a shell) starts receiving. Transfer → Cancel Transfer stops a transfer on both sides.
All four protocols are built in, on Linux and Windows.
Tools → Import BBS List… reads your SyncTERM dialling directory (syncterm.lst), shows what it found and adds the BBSes as sessions with the BBS settings. RLogin passwords in the list can be kept as credentials in the password store.
Saltbush runs SyncTERM-Lua scripts unchanged. See scripting and the experimental LORD and TradeWars bots on the download page.