Question, have you made sure that they are compatible? Not all keyboards work with all tablets (although it is assumed they would). If you did make sure of this, then to pair them try the following.
Wireless Bluetooth
Linking or pairing a wireless keyboard can be easy, or difficult, depending on a few different factors.Factors like the operating system of the tablet and the brand of the keyboard.
For tablets that have built-in Bluetooth capability you should be able to use the steps below to pair them. This is general pairing information. It may vary slightly for different brands or different tablet OSs (Windows, Android, iOS, etc.).
To pair the keyboard to the tablet.
1. First, make sure the wireless keyboard has new batteries...