You will need to create an NFT 'Collection' which is where your minted NFT will be stored in.

Click on your profile name at the top of the page.

You will then need to click on 'My Collections'

Click on 'Create a new collection'

You will be presented with a new page that allows you to fill out the details of your collection. Note: The more information you provide the better it is for collectors to understand your artwork. Also, it makes verification of your profile quicker.

When you have saved your collection you can now Mint your NFT.

Click on 'Mint NFT' in the top bar of the website

You will now have a page that allows you to add the NFT project details and upload everything ready for selling. Below is an example: