The MOST important thing to know is that pattern sizing is not the same as high street shops sizing.
If you are a 10, say, in M&S, Next etc, there is a good chance you will be sewing a pattern size at least one size up, and probably 2 sizes up. DO NOT LET THIS MEAN ANYTHING TO YOU MENTALLY!
Aside from that, independent pattern makers will often have their own pattern sizing.
So, you need to know your measurements.
Read up on fitting. You might need to learn about adjustments, you might not. Measurements will tell you!
Purchase 1 - a tape measure!
Then you'll need good fabric scissors, a seam ripper and decent pins.
Practice sewing straight lines on some old sheeting or other scrap fabric.
Lastly, nothing is impossible!
Oh, and put a piece of scrap paper under your presser foot when changing a needle. Then you won't drop it into your machine!