How do I add products to my shop?

Short answer: Two steps: add the product to your selection from the catalog, then drag it from the selection into a collection of the shop.

Steps

On the “Shops” page, open a draft of the shop — a live shop cannot be modified directly (orange “Modify the shop (create a draft)” button). If you are already on a draft, skip this step.
Click “Catalog” to open our general catalog.
Click on the product you are interested in. Its detail sheet opens: choose its colors — up to three — then add it to your selection. See How do I choose the colors of a product.
The product joins your selection straight away, shown in the panel on the right of the catalog: there you check, without leaving the page, that everything you wanted is in. Keep going through the products while you are there.
Go back to the dashboard, where the same selection fills the left-hand panel. Grab the thumbnail of the product — anywhere on it — and drop it into a collection of the shop.
Save, then put the draft into service when everything suits you.

Step 5 is the one people forget

A product added from the catalog lands in your selection, not in your shop. Until it has been dropped into a collection, it is visible nowhere to the buyer.

If you have added products and the shop seems unchanged, it is almost always this: the drag and drop has not been done. See Catalog, selection, collection — what is the difference.

The selection is shown in two places, but you can only drag from one

It is the same list in both cases. On the right of the catalog, it serves to check what you have just kept. On the dashboard, on the left, it serves to fill the shop: that is where the drag and drop starts from, and only there — and only on a draft.

Products that exist in several versions (Men, Women, Junior) are added to your selection together, and are dropped into a collection together. See What is a multi-version product.

While editing, clicking a selection thumbnail serves only to drag it. To open a product's detail sheet, click the small (i) icon at the top left of the thumbnail — see I click on a product and its detail sheet does not open.

Going further

How do I organize my products into collections — creating, renaming and ordering collections.
How do I put my logo on a product — marking the product once it is in place.

You'll know it worked when: The product appears in the collection you chose, and the collection counter has gone up.