Go to Schema Pro → Schemas → Add schema and pick a type. The picker groups the 30 types by purpose and has a search box, so typing recipe or job gets you there quickly.

Each type opens an editor with four panels:

Properties — the schema's fields. Most are filled in automatically from the post being viewed, so you can usually leave them blank.
Where it applies — the targeting rules that decide which pages get this markup.
Search Preview — an illustration from your markup.
Output Preview — the JSON-LD that will be produced.

Save, then visit a page the schema targets and view source. You will find one <script type="application/ld+json"> block in the head.

Addresses are kept as you paste them, % codes and all, in the rows of a list too: an Item List's Link and Image and a How-to step's Image, as well as every address field on its own. A javascript: link is not kept. A list link or image saved by an earlier version lost its % codes, so a page whose address has an accent or a non-Latin letter in it was saved as another address; paste it again and save.

Delete, beside Edit on the Schemas list, asks before it deletes, because the schema's markup leaves every page it covered at once. Only an OK to that question deletes it. Opened any other way, in a new tab, with the middle mouse button or from a link saved earlier, it deletes nothing: the list asks again, naming the schema, with its own Delete button and Cancel. Without JavaScript, that is the question you see. A Delete for a schema that is no longer there, from another tab or an old link, deletes nothing and the list says so.

Adding your first schema