The where to find pattern part is easy. www.knittingpatterncentral.com
As for casting on, it's amazing how many stitches will fit on a standard needle. For a large number of stitches it's good to use a circular needle and use the two points to knit back and forth.
A swatch is a sample of your knitting tension on the needles and yarn to be used for a pattern. It is only truly important when a garment has to fit. You can be more flexible with a blanket--it's ok if it turns out bigger or smaller than the pattern, same with scarves, washclothes and the like.
Every pattern lists a gauge. That's the number of stitches per inch you need to come up with in order to get the same size as the pattern lists. Since we all knit at slightly different tensions, we knit up a swatch--about 5 inches by 5 inches and measure how many stitches we get over 4 inches of it. If it matches the pattern, great. If not, you can change needle size to get the proper gauge.