no connection with Broadcom BCM4311 802.11b/g WLAN wireless card

Since I installed Lubuntu 18.04.3 recently (on a Lenovo 3000 N-100 notebook) I have no wireless connection. I’ve read several previous AskUbuntu questions. Regarding the first answer to the AskUbuntu question at, I believe I followed the section titled Installing The Package (Online). There is still no wireless connection. Here is a current screenshot of the system tool Software and Updates. enter image description here

If you can help with suggestions, please make them clear and complete, step-by-step, without unnecessary assumptions/jargon/etc as I’m relatively new to Linux, and my awareness of system architecture and software is quite limited. Thank you.