First, forget about solutions using iwconfig (which does not support WPA) or wpa_supplicant. They are outdated.

Modern (post-2010) Linux distributions use NetworkManager to manage network connections. nmcli is the command line interface to NetworkManager.

This tutorial assumes that your WiFi adapter has been properly driven by the Linux kernel.

Steps:

Make sure NetworkManager is running (It should be on if you boot into a desktop environment. But it may not be running by default if you are in the non-GUI mode of Linux.)
```
systemctl start NetworkManager
```
Scan for available WiFi networks
```
$ nmcli device wifi list
```
You can pipeline it with the less command if you have a long list of WiFi access points (APs).
Connect to a WiFi network for the first time (If this is not the first time, jump to step 3).
```
sudo nmcli device wifi connect NETWORK_SSID 
```
where NETWORK_SSID is the ID of the network.

If the network is password-protected, you can pass the password verbatim like this:
```
sudo nmcli device wifi connect NETWORK_SSID password "NETWORK-PASSWORD"
```
Or, if you prefer not to leave your password in your shell history, you can use the --ask flag to be prompt to enter a password.
```
sudo nmcli device wifi connect NETWORK_SSID --ask
```
The information of each network (called “connection” in NetworkManager’s terminology), including the password, is stored into a configuration file under /etc/NetworkManager/system-connections/. That’s why you only needed to do this step once, when you initially connect to a WiFi. Otherwise, nmcli will create duplicates for you.
To connect to a network that was previously connected to, simply
```
nmcli con up NETWORK_SSID
```
Check your connection. You can simply check your connections by
```
ping google.com
```
Disconnect from a WiFi, if you need to:
```
nmcli con down NETWORK_SSID
```
Auto-start NetworkManager at system book (only for non-GUI boot) NetworkManager is a GUI program and is usually started when the desktop environment starts. What if you Linux box is configured to boot into non-GUI mode as in a server? Simply enable NetworkManager in systemctl.
```
sudo systemctl enable NetworkManager
```

Additional fun

You can use ifconfig or iwconfig (for wireless only) to identify all your network interfaces. Then use iwlist to scan to know more information of the networks available around your.

$ iwconfig

The output is

lo        no wireless extensions.

wlp0s20f3  IEEE 802.11  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=22 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on

As you can see, wlp0s20f3 is the wireless adapter on my computer. Then I just need to run

sudo iwlist wlp0s20f3 scan

to find out detailed information about WiFi networks available around me.

References

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/networking_guide/getting_started_with_networkmanager#sec-Overview_of_NetworkManager
https://www.makeuseof.com/connect-to-wifi-with-nmcli/