If you are wanting to use the credit card processing capability built into RMS, you don't need any other software.
On your magnetic stripe reader, how does it connect to your system? If it's the "keyboard wedge" type (attaches inline with your keyboard) it should work without doing anything. When the credit card # window pops up in RMS, just swipe the card through your MSR and it should pick up the card info and away you go. Just to make sure the MSR works right, open up a notepad session and swipe a credit card, you should see the data in the notepad window.
The other piece you have to do is enable EDC in RMS. First you need to tell your credit card processor that you need a "Vital Network Setup Sheet". This will give you all the info you need to put into RMS. Just look through this forum and you will see several entries on it.