Yes, you can do that. Via the JBL Connect app or as described below!
For pairing to work, one of the JBL speakers must be connected to your smartphone via Bluetooth. So turn on Bluetooth on your smartphone and then press the power button on the JBL speaker.
Your phone should recognise the speaker as an available device and connect to the speaker via Bluetooth.
Next, turn on the second JBL Bluetooth speaker you want to pair with the first. Now press the Connect button on both speakers. After a short time, the two speakers are paired.