Do not under any circumstances pirate a First Aid course. Even if you learn the material completely, you'll have no legal protection if/when something goes wrong. Moreover, much of the material requires hands-on training, not something you can learn from a book or article.

If you want the certification and course, check with your employer. Many will enroll you on their dime since they need a certain number of staff to be certified at all times. It's typically a 2-4 day course and you're paid your salary while doing it.

I'm First-Aid CPR/AED certified. If I see someone in need of help I have certain protections the general public doesn't. Mainly that person can't sue me for breaking a rib, causing an AED burn, etc.

Note: This is accurate for Ontario, Canada. I'm sure other Western jurisdictions work similarly.