Anyone can join the Catholic Church, as others have said already. However, also as some have mentioned, this is not just a question of ticking a box and signing up.
If you just want to attend the Sunday Mass, or even the daily ones during the week, there is absolutely nothing to stop you.
You will hear the Bible readings and homilies that hopefully explain quite a bit about the Christian faith, and following the prayers of Mass will help you enter into the mystery of following Christ.
However, don't go up to receive Communion until you have been formally received as a Catholic as this would be a sign that you knowingly accept and understand the full teaching of the Church.
Just as others have said, ask the priest or deacon about how one formally becomes a Catholic. He might suggest some good books to read and maybe a parish group that you could meet to get to know other people better and explore the practical aspects of faith.