I don't have the version downloaded anymore, but if I recall, the readme.txt starts off by telling you to choose either install or install_ubbcodebuttons (if you want to keep your ubb code buttons). Once you install those, you've got a separate set of instructions for your wordlets. Just open all the text files and that should help you find which ones you need to start with.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.