Q: a wifi connection was save with wep security and i need to change it to wpa2/personal security

I have at home a new wifi connection and I don't know what happened that it was saved with a wep security instead of a wpa2/security, this brings me problem with my wifi connection it last a lot and a sign appers telling me that: "That connection was saved with wep security do you want to connect?"

How can I solve this problem?

Thanks

Laura