Go to sold items in eBay and look at the order.

If the buyer has paid then you can post.

There should be the address to post to and send.

Otherwise you need to wait for the buyer to pay.

You will have a hold on funds if you are a new seller.

(Looking at your sold items, you have sold before so would now how eBay works)

You need to post within your handling time and not wait for the funds to be paid out

Did you fully complete sign up to Managed Payments and be verified to sell before listing? 

Have you read up about the holds on your funds, they are usually 30 days for new sellers 

If it’s been some time since you last sold, you are now classed as a “new seller”.

Are you verified for Managed Payments?

https://www.ebay.com.au/help/selling/getting-paid/registering-seller?id=4792

You need to post out the item by the date specified in your postage & handling terms. If you don’t, your account will get a black mark, and in addition eBay won’t disburse the funds to your nominated and verified bank account prior to that, and there will be the additional “hold” period as well.

Make sure you are fully verified (both bank account and ID) as required, or you’ll never receive your funds.