You can download a manual for your White machine from the Singer website, link is
Here are the relevant pages from the manual:
Straight stitch settings as follows:
stitch length on 2.5 (selector marked with blue arrow)
stitch width on zero (no swinging of the needle) selector marked with red arrow
stitch selector on A - selector marked with green arrow
Generally all sewing machines will have a similar three controls, because all stitches are a combination of moving the fabric forward a certain amount between the needle going through the fabric - the stitch length; and moving the needle from side to side - the stitch width.
And then a stitch selector for different stitch forms such as a blind hem or shell stitch where the needle is going through a series of different moves in sequence to form a special stitch. You still have the width and length controls to vary this formation.
For general sewing machine information www.sewing.about.com
is excellent, there is lots of pages on general tips, cleaning, threading up and sewing machine know how. Try this page to start http://sewing.about.com/od/sewingmachineindex/ig/Sewing-Machines.--9k/
If you are a beginner, then I'd recommend printing out the instruction manual for your machine and putting into a binder, placing beside the machine, and carefully read from the beginning going through all the instructions to wind a bobbin, thread up, three or four times until you can do it without reading the manual, then practice stitching out each of the stitches your machine does. Buy a cheap exercise book and on each page, write the name of the stitch, staple the stitch sample in and either write down the settings used or glue in a photo taken of the machine controls you used. This way you can quickly flick through and refer to your settings next time. ADjusting the top tension dial will also adjust the stitch formation so read the manual and set the tension dial to the setting it suggests but sometimes you'll need to adjust it slightly to get the stitch looking even (balanced between top and bottom thread), especially for zigzags.
Practice a bit and you'll soon feel much more confident using the machine. Also, refer to the cleaning and oiling instructions and do it regularly, along with changing the needle for each new sewing project, about 4-6 hours sewing time. The needle is the most important part of a sewing machine, always use the right sized needle for the fabric. Refer here for info http://sewing.about.com/od/sewingmachineindex/ig/Sewing-Machine-Needles/
I hope this helps you with your White sewing machine, there are lots of great sewing machine books on the market too or in your public library to refer to. Also taking beginner sewing classes will really help you learn how best to use your machine. I've been sewing for over 38 years but still enjoy going to a class and learning a new technique from another enthusiast - life long learner!!