You can tell the weight of the yarn several ways. Here's a link that might help.
The yarn called for in the pattern is a 1 or fingering weight yarn. The yarn you chose is a 4 or worsted weight yarn. So as Sue says you need to either get a different yarn or a different pattern to match your yarn.
What you try to do when substituting yarn is get as close to the same gauge as possible so your project will come out the same size. Each persons knitting can vary so you may need to go up or down a size from the suggested needle to get gauge. That's why you're making a gauge swatch or sample.