https://www.shopify.com/guides/dropshipping
Fair warning though: you'll still have a ton of problems and spend time dealing with customers.
For example, the first time I got a $100+ sale on an item, I went to ship it and found that the vendor took the product down from AliExpress... but my Shopfiy account didn't update to reflect that.
So there are tons of pitfalls and things to be careful of, but like any field, you need to experience them firsthand, it's just part of the process. You can make money at drop-shipping, but it really is not easy, and there's still risk involved, like any business.