Your listing can be offline for several reasons:
- the quantity is 0
- the price is 150% of the new price of the product
- you haven't selected a shipping method for this listing yet
- the comment is not set or not translated in the right language
- you have reached your sales threshold for the day
As soon as the information is filled, the listing can be either online or pending validation, if it has been attached to a product you created. If you want to know more about that, you can read the article Why is my listing under validation?
If you want more information on how to set up shipping methods, you can read the article How can I set up my shipping methods?