WiFi - Activation of network connection failed

Hello everybody,
today I have started my very new experience with Linux. I have installed Zorin OS on my pretty old notebook HP 620 (via ethernet) and voila - the first problem is here. When I try to connect via wifi, there is a error message “Activation of network connection failed” and I don’t know why.
Please, could anyone help me to find and install drivers for Realtek Radio Model RTL8191SE? Thank you.

Hi, aish.cz.
For your message, can you try this?
If those suggestions don’t work, try sudo apt-get install --reinstall network-manager in terminal (ctrl+alt+t). But first try the appuals suggestions.