If you are only sewing garments and in particular, knits why do you need your machine to be compatible with your PC? It should not be necessary unless you wanted to stitch out digitised machine embroidery patterns, something I've never done in 30 years of dressmaking.
To sew knits you need ball point needles, in an appropriate size for the fabric weight. Good guide to sewing machine needles is here - http://sewing.about.com/od/sewingmachineindex/ig/Sewing-Machine-Needles/
On knits you need either a very small zig zag stitch or your machine may have a stretch stitch where the fabric is moved forwards and backwards a little to put some stretch into the seam. Also use polyester thread. You need the ballpoint needle as it pushes between the fabric fibres rather than piercing them, imporant with knits to prevent the seam from popping/breaking when under stress.
For hems you can use a twin needle on the top of the fabric, this gives a nice finish to the seam and also some elasticity as the underneath bobbin thread forms into a zig zag to connect with the twin needle on top.
I would suggest that you visit the www.kwiksew.com
website or this link
for lots of quick sewing tips for knits like attaching rib jersey for necklines and cuffs that speed up the sewing and give results similar to ready to wear. I bought their "Sewing for Toddlers" and "Sewing for Children" books and traced off patterns for PJ's, track pants and sweat tops and made loads of clothes for my boys from this one book, it is a great resource for knit sewing. They have other books too for adults.
Anything you need in terms of selecting stitches on your sewing machine should be in the instruction booklet, but how you use those stitches and assembly garments is best learnt from taking sewing classes or a good sewing book.
Other useful websites for sewers are www.sewing.about.com
, www.patternreview.com www.burdastyle.com
- there is also a yahoo user group called "FuturaEmbroidery" of fellow Singer Futura sewing machine owners that you may wish to join, often can pick up lots of helpful info and advise from fellow owners.