If you don't have time to read the tutorial, here is the quick way about it.
Select what view you want your reference image to be in. For example if it is a front view of your object, you would want to set it up in your front viewport etc. Begin by going into your Hypershade, and selecting the tab entitled 'Cameras'. Middle mouse Button drag the Viewport you want to attatch an image plane to into the bottom workspace of the Hypershade. Next go to the "Image Plane" tab on the left of the Hypershade window, It is near the bottom of the list. Drag an image plane onto the viewport you have put in the workspace of the Hypershade with the MMB. A menu should pop up that asks what connection input you want, select default. With the image plane still selected in the Hypershade, go to the attribute editor, and click on the little folder icon next to the "Image Name" field. find the image you want to use as reference and open it. Now you are all set, close your Hypershade and look through that viewport that has the image plane attatched, and you are ready to go.
Note: there are other ways to do this, so if this is confusing or you just don't like it, look around for other tutorials.