This article explains how to pair a Bluetooth speaker with your iPhone or Android smartphone. Some Android buttons and menu options may differ slightly.
How do I connect my Bluetooth to my phone?
The process of pairing a Bluetooth speaker with an iPhone only needs to be done once. Once a Bluetooth speaker is successfully paired with an iPhone, it should automatically connect every time it is turned on.
Put the Bluetooth device into pairing mode.
Open the Settings app on your iPhone.