LaTeX:The Not So Short Introduction to LaTeX2e
Original Source for the TeX guide: http://tobi.oetiker.ch/lshort/lshort.pdf

Here is a good link for help with xypic and knots: XY-pic tutorial by Aaron Lauda.
xy-pic uses a coordinate system for everything that it does. When he has the code: (6,9)*{}="1"; This means that he wants xy-pic to label for future reference the point with coordinates (6,9) with 1. From now on, he can refer back to it by typing "1". If he wanted something to show up there, then he would have typed: (6,9)*{something}="1";

Download Tex
Apple	MacTeX - TeX Users Group for Macs This website will have the installation information for the bundle including TeXShop (the preferred front end for Macs) and MacTeX (the background program that does the rest of hte work).
Linux and Windows	Step 1: Instructions for downloading and installing MiKTeX (You can use either the standard or the complete version. The complete version has more features but takes longer to download.). Step 2: Go to this website and follow the instructions for Texmaker.

To include a dictionary, download one from here or a different source, open your tex compiler (if Texmaker, use Configure Texmaker -> Editor -> Spelling Dictionary and then select the downloaded dictionary.).