I get the error message (ie given below) on installation of any rpm file in openSUSE.

[PK_TMP_DIR|dir:///var/tmp/TmpDir.NUXK6P] Repository already exists.

What should I do?

Sounds like the package has been installed before or you have attempted to install it before. You can clear the file and try again

This is a known issue with openSUSE 11.0+. Essentially it is a fault with the software manager application. So far I have been unable to find a solution other than to redo the system and dis-allow "Software Updater" to manage my system.

Go to terminal...

Cd <location of your downloaded package>

Then

Sudo zypper install <package exactly name e.g skype.2.2.03.4.rpm>

It will install it for you...