yum install glibc.i686
install this.
You did not mention what the command was that you were trying to run that produced the error message. However, the bottom line problem is that you are trying to run and/or install 32-bit (i686) packages on a 64-bit (x86_64) system which is not a good idea. For example, if you were trying to run the 32-bit version of Perl on a 64-bit system, the result would be something like
perl: /lib/ld-linux.so.2: bad ELF interpreter: No such file or directory
If you still want to use the rpm command to install the 32-bit versions of glibc and glibc-common on your system, then you need to know that you must install both of the packages at the same time and as a single command because they are dependencies of each other. The command to run in your case would be:
rpm -Uvh glibc-2.12-1.80.el6.i686.rpm glibc-common-2.12-1.80.el6.i686.rpm