If you press the paging button on the front of the Yealink base station this should page the IP address on the phone screen - please see the screenshot below to show where the paging key is located on the base: 

Another option to find the IP address on a cordless Dect phone is to: 

1. Click OK on the phone's keypad

2. Click OK on the (i) icon

3. Click OK on the BASE option

4. The IP address of the Base will then be displayed on the phone's screen.

Alternatively you can obtain the IP address via the Settings on the phone handset. 

Select Status 

Select Base Menu

This should then display the IP address on the phone screen.