GNU/Linux Ubuntu 18.04 Realtek rtl8821ae Driver Installation Guide
The linked tutorial shows you step-by-step How to Install Realtek rtl8821ae Wireless Driver for Ubuntu 18.04 Bionic LTS GNU/Linux – Step by step Tutorial.
And the Realtek rtl8821ae Ubuntu 18.04 Driver Installation is Quick & Easy, involving at most the execution of some Basic Shell Commands.
Finally, if you have Different Card then See this Other Guide: How to Install Realtek Wifi Drivers on Ubuntu.

Installing Realtek rtl8821ae Driver Ubuntu
How to Install Realtek rtl8821ae Wifi Driver for Ubuntu 18.04
Here Ubuntu Realtek rtl8821ae Installation