Hi, I’m new here and I would like to know where can I see the descriptions or authority that letting me to remix their songs. Since I just read that some owner might won’t let you transform their work.

Every tune in ccmixter has a licence, this is shown in words and as logo. Three main ones are used.
Attribution 3.0 Unported (CC BY 3.0)
Attribution Noncommercial (3.0)
Attribution Noncommercial Share-Alike (3.0)

For each tune click on the logo to go read the licensing terms.
Please read the part where it says Adapt.