After a basic installation, additional programs and services are often needed. This can easily be done with yum.
Yum gets software from your version repositories over http. It also manages dependencies and installs them too.
Before installing it is best to first find out which file you actually want. This can be done with:
yum list <program>
Not always will a program name be exactly known. Then wildcards can be used before and/or after the program name.
yum list *<program>*
In such case multiple variants from different repositories of the program can show up. Choose the one from the most stable repository: base. Other repositories like devel are less stable.
Sometimes the program is part of another installation. To find it in such case, you can use the provides command.
yum provides */<program>
The */ part is sometimes necessary, at least in Centos 6.
When installing, type the exact name of the program (without the version number part). And never use wildcards with the install command.
yum install <program>