Linux Mint uses a Network Manager icon in the lower right of its system tray panel to manage network connections. If you are connecting to the Internet using an Ethernet cable, wired connection, it should be automatic. If you are using WiFi, then you have to click that icon and select the WiFi router that you want to connect to and provide its password.
A lot of WiFi adapters are automatically recognized by Linux Mint, but not all of them. USB WiFi adapters that are known to automatically work with Linux Mint without updating or compiling drivers are available from around $10 and up from Amazon.com, Ebay, local electronics stores, business supply stores, etc...
In the years I have been using Linux Mint, I have never had any problems with it automatically connecting to a wired ethernet connection unless the Ethernet port is bad or has gone bad, or a bad ethernet cable, and you can easily get a USB ethernet adapter or another ethernet cable for that as well from the various places described before.
Once in a while with a new installation of Linux Mint 18.x while booted into Linux Mint, I have had to remove a USB Wifi adapter wait 10-12 seconds, and re-insert it for it to recognize it the first time, or run the command below from a console terminal and wait a little for it to restart and rescan available network devices.
Code: Select all
sudo service network-manager restart
Hope this helps ...