htop is a good option to monitor your system interactively. In order to install htop, you will need to use dnf. If you cannot install htop by yum, you will need to follow following procedure on CentOS 8.
STEP 1. Enable the EPEL repository
# dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
STEP 2. Update the system after the installation of the EPEL repository
# dnf update
STEP 3. Install htop
# dnf install htop