How and when can I edit my listing?

The simple answer is whenever and as often as you like. Go to My Listings within your Dashboard and click Edit next the listing you'd like to edit.

Of course when you accept an Ordering Request, you must provide your service or product as per the description at that time, this is shown and logged within the Order Request, so everyone knows what was agreed.

Once you Publish your listing it will may not be visible immediately to everyone on GivYo, this is because some moderator checks may be taking place, for example making sure photos meet the guidelines. Any feedback about your listing will be shown in the message center.