1. Read
Nicky Cake's noob guide
2. Read the stickied posts in the Newbie Questions forum and the affiliate marketing forum.
3. Set aside some money to spend to start understanding affiliate marketing. Could be $100. Could be $500.
4. Apply to an affiliate network. I like Ads4Dough.
5. Buy a $100 Facebook Ad coupon in the Buy & Sell forum. Start testing. Keep testing. Pick an affiliate offer off of your affiliate network and make two ads for it. Which gets more clicks? Which gets more conversions? That's split testing. Now kill the ad that is performing poorly and make a new ad. Keep doing this until you have an ad that is performing well. What's performing well? I don't know. Keep testing until you start thinking you know what's going on. Then keep testing until you realize you aren't hot shit and start asking questions.
Keep asking questions. At some point start reading less and trying more. Aim for breaking even in your campaigns. How much should you be spending? Not a lot, but not more than your comfortable with. Keep trying things out. Don't take what you're reading at face value - test it. People will say lots of things work and lots of things don't. Maybe they're wrong. Maybe they're right. Test it and figure out what works.
There isn't an easy solution to this. These isn't a magic formula to understand affiliate marketing and make $1000/day overnight. There is a lot of hard work. A lot of wrong ends. A lot of testing. A lot more testing. And a lot of thinking.
So start by applying to a network, reading Nicky Cake's Noob Guide, and reading through the stickied threads. If you have a question, search the forum. If you don't find an answer (or don't understand the answer) ask a question. Be specific. Be concise. Be on topic.
Breaking into the affiliate marketing 'game' is easy. What's takes a lot of work is understanding what you're doing, getting to a break even point, and starting to
do instead of read or think about doing.