OP, my manual for a Panasonic says :
Press ok
Setting HS (handset)
Registration
Register HS
Press and hold (find) button on the base unit for 5 secs
Select base unit number
Wait until "BS PIN" is displayed
Enter the base unit pin(default "0000")
When the hand set has been registered correctly the (wireless icon) stops flashing
If still flashing start again
Not sure if your phone is the same but I hope this helps