GNU/Linux Mint 19 Realtek rtl8192CU Driver Installation Guide
Hi! The linked Tutorial shows you Step-by-Step How to Install Realtek rtl8192CU Wireless Driver in GNU/Linux Mint 19.x Tara/Tessa/Tina/Tricia LTS.
And the Realtek rtl8192CU Mint 19 Driver is already bundled in the Latest Linux Kernels.
Finally, if you have Different Card then See this Other Guide: How to Install Realtek Wifi Drivers on Ubuntu.
Installing Realtek rtl8192CU Driver Ubuntu
How to Install Realtek rtl8192CU Wifi Driver in Linux Mint 19
Here Ubuntu Realtek rtl8192CU Installation