Hi, I can't share internet connexion to usb port

That is not supported. What you can share is what is on the list of supported ports. If you have an Internet device connected to a USB port that is listed in Network preferences as active, it may appear on the list but I'm not sure that is correct.

As Kappy has pointed out, you can basically only share an Internet connection with ports that appear in the "To computers using" list. Unless you have some type of networking device connected to your Mac's USB port, it can't be shared.

For example, when I attach my iPhone to my Mac's USB port, it shows up in that list as: iPhone USB. However that would only give the iPhone Internet access. It would not allow the iPhone to perform as a hotspot. I do not have a USB wireless adapter to verify that you can share Internet access to it ... but it should and would disable the Mac's internal Wi-Fi doing so.