How do I update my hds 5x

[S13Blaz]

I just bought a boat that has an hds 5x on it and I have an hds 7 that I want to add to the boat. I tried to connect with an Ethernet cable and it tells me to update with the same software. I am trying to get the hds 5x updated so they can communicate. I have the software on a card but cannot get the 5x the take a download from the chip which is in the 7. I read that you need to press and hold the up arrow then press the power and release and hold the up arrow until the update starts. Well the power button is also the light button which won’t let it start an update. What am I doing wrong?  Any help would be greatly appreciated.