I have install lubuntu 19.04 but i don’t found how to connect to wifi please help
Read the Ubuntu 19.04 documentation for help with this kind of query. The help page you want is here: https://help.ubuntu.com/stable/ubuntu-help/net-wireless-connect.html.en
This is something I wrote for 18.10, which you may find helpful.
Sorry - I’ve just checked these instructions and they are probably not very helpful. There should be an icon on your toolbar for wifi/connection - click that and choose your router.
There’s also the possibility that proper drivers aren’t loaded. You can run
lspci and if you see Broadcom’s name in there under the wireless controller, that’s likely your problem. Instructions to fix it can be found on the Ubuntu wiki.