There is no option to enable coldcard on the Electrum plugin it's enabled by default.
The only problem is he uses the Portable one which doesn't have the Coldcard plugin and other plugins do not work on Electrum portable.
No idea really how it works. I have never used ColdCard nor did I need to play around with those types of settings. I was only mentioning some of the points I found important from ColdCard's documentation. If the portable Electrum client doesn't even have the required plugin, the guide should mention that. It could just be another sentence or two informing the readers which version of the app they need to use and which one won't work.