Place the negative to be enlarged in the negative carrier of the enlarger and with the enlarging lamp on, and the lens set at maximum aperture, adjust the height of the head so that the image fills the size of the paper you intend using. You will find it easier to do this if the normal light in the room is now turned off.

When you use a focus finder it magnifies the grain so it is easier to see when the image is sharp. You will see the grain structure when the image is perfectly focused.

Now you can make a TEST STRIP!!!