I want to add options at checkout where the customer can choose items that come with the product.
For example - Bracelet and choosing 3 free charms that come with it from a list of charms.
Right now, shopify only gives option where I can put sizes. Is there a way to add more options at checkout?
Means you want to add upsell product when checkout. This is a very complex request, you need to have experience with Liquid, CSS and JS.
If you have no experience, I recommend you to hire a professional.
Hope it helps!