Hi, welcome. There are no secrets to a clean eating diet plan. Eating clean means avoiding processed foods. Read labels, even when you think you're buying something healthy. For example, I buy a lot of kidney and black beans in a can to toss in my salads. However I found out that most brands have a whole load of sodium in them. So I switched to Eden Organics which have 0 sodium.
Eating clean means eating mostly whole foods. Make things from scratch. When you shop at the supermarket shop from the perimeter, that's where the produce and refrigerated sections are, aka perishable foods. Shop very little from the aisles where the pre packaged foods are.
"No matter how developed you are in any other area of your life, no matter what you say you believe, no matter how sophisticated or enlightened you think you are, how you eat tells all." - Geneen Roth