Start by installing the program and learning how to open it.
Select an image to rectify: You might as well start with one of the samples included with the distribution. (ASRix v2.x can work with .JPG, .TIF and .BMP files with an 8 or 24 bit colour depth)
Open the image using the icon on the toolbar or the File->Open menu item.
Maximize the Source Window and zoom until you can see the points for which you have real world coordinates. F10 zooms in F11 zooms out and F12 will fit the image to the available space. If you have a wheel mouse rolling the ball can do the zooming.
Map Points on the image to points in the real world:
Move the cursor near one of your points and double click. You will be presented with the Point Mapping dialogue Box where you can fine tune the placement of your point and enter the values for the coordinates of that point. Then Click OK and repeat for the rest of the points for which you have coordinates. (A minimum of 4 points are required)
To move a point:
Click and hold the left mouse button when the cursor is on the point and drag it into place or, while holding the mouse button, use the cursor keys to move the point in 1 pixel increments. This works the same in both the Source Window and in the Point Mapping dialogue box.
If the point is difficult to see:
You can adjust the colours of things from the Properties dialogue box.
When all your points are correctly placed click the rectify button on the toolbar or the Tools->Rectify menu item to rectify the image.
If your points were good you will have a rectified image, if your points were not good you will have something else and you should look at the section on Trouble Shooting to figure out what went wrong. (Usually it's points out of order or bad measurements in the field)
The first step in understanding how the ASR Rectifier works will be getting to know the help facility and after that an understanding of the toolbar, the menus and the various input methods will get you ready to tackle the section on using the rectifier and start using ASRix on your own material.