hmm... are you able to find the minecraft folder at all? the jar file should just be in the "bin" folder. For a much easier way, you may consider browsing the packs available in the Techinc or ATlauncher, as all you need is a minecraft account to log in. You can choose from a large selection of mod packs with various themes and difficulty levels, and the tedious setup process for utility mods like forge, NEI, etc are usually done for you. From there, any mod you'd want to add would just go in "mods" in the main minecraft folder, and playing a pack with mods you wouldn't have thought to add yourself adds to the fun of discovery.
Does that help?