First of all, while the hardware and accompanying software differ, almost all card readers that you attach to a regular computer function in "keyboard emulation mode". That means that the data will be received by your computer as though a very fast typist typed it all in. You can put the cursor in a text field on your layout, swipe the card and all the data from your card appears in the field. From there calculations in fields or scripts like those shown in the knowledgebase article can be used to extract different chunks of the scanned in data.
Please note that each type of credit card uses a different format for this data so you have to identify the type of card (if more than one type needs to be scanned) and then you select the appropriate set of caclulations to extract the data.
In addition, the software that comes with you scanner will likely enable you to specify text to put at the beginning and end of the scanned text. You can use such text to trip script triggers to perform scripts that respond to and process the scanned data.
Here where I work, we scan the mag strips on Drivers Licenses. The scanners are configured to precede the scanned text with Shift, caps lock ~ and an onKeystroke trigger performs a script that checks for this text. If it's detected, it uses go to object (Go to field works also) to put the cursor in a text field. The text at the end of the scan happens to include the Enter key and field behavior settings on this text field respond to this key by exiting the field. Thus, an OnObjectExit trigger performs a second script that parses all the scanned data into appropriate fields, while performing tests for damaged mag stripes etc.