This summary is not the rule. The rule text controls.
If you're named as the executor in a will, you need to ask the court to officially confirm you in that role before you can start handling the estate. This rule explains when and how you can make that request.
You can file this request after the will has gone through probate, which is the court process that verifies the will is valid. If the will is a special type called a nuncupative testament by public act (a will made orally in front of witnesses and a notary), you can make this request after it has been formally presented to the court instead.
Once you file your petition asking the court to confirm you as executor, you can also ask for letters testamentary in that same document. Letters testamentary are the official papers that give you legal authority to act on behalf of the estate, like accessing bank accounts or selling property. This means you don't have to file two separate requests. You can combine your request to be confirmed as executor with your request for the paperwork that lets you actually do the job.