I bought Minecraft yesterday and had so much fun. I heard about skins from my friend and decided to change it. I went to minecraft.net and tried to log-in, but I couldn't. I logged in succesfully at account.mojang.com though. I also bought Minecraft at account.mojang.com too with a gamecard at Walmart. How do I migrate my mojang account to Minecraft?
You would not "migrate your mojang account to Minecraft," your Mojang account is your Minecraft account. Log into minecraft.net using your Mojang account. Make sure to use your email address as your username. If it's still not working, check that the servers are up. https://help.mojang.com/
Mojang appears to be having trouble with their servers right now. You might want to wait and try again later when their servers all show green.