Besides using yum-config-manager or the dnf config-manager command, you can also select a release series by editing manually the /etc/yum.repos.d/mysql-community.repo file. This is a typical entry for a release series' subrepository in the file:
[mysql57-community]
name=MySQL 5.7 Community Server
baseurl=http://repo.mysql.com/yum/mysql-5.7-community/el/6/$basearch/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql