If you like what you see, please donate some BTC to bc1qf3gsvfk0yp9fvw0k8xvq7a8dk80rqw0apcy8kx or some ETH to 0x7e674C55f954d31B2f86F69d7A58B2BCe84Cf6b4

A simple no non-sense guide to deploy your NFT on Ethereum and have it automatically displayed on OpenSea.
References:

• We will use Metamask to fund the smart contract deployment
• We will use Remix to code the smart contract - and deploy it
• We will use OpenSea to display our NFT - Metamask will be used to log in
• Our NFT will be saved on IPFS via Pinata
• Finally, we will use Rinkeby as a test network

We will use the code provided by OpenZeppelin:

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract AcmeNFT is ERC721URIStorage, Ownable {
    using Counters for Counters.Counter;
    Counters.Counter private _tokenIds;

    constructor() ERC721("ACME", "ACM") {}

    function awardItem(address invitee, string memory tokenURI) public onlyOwner returns (uint256) {
        _tokenIds.increment();

        uint256 newItemId = _tokenIds.current();
        _mint(invitee, newItemId);
        _setTokenURI(newItemId, tokenURI);

        return newItemId;
    }
}

In the code above 'ACME' is the name and 'ACM' the symbol.
The 'awardItem' function will be invoked to 'mint' a token, or associate a token to an address 'invitee'.

Using your artistic skills, design a movie, image or animated image. This is mine (I used PhotoFunia on one of my pics):

We need to store the design as well as some metadata. Several options for storage are possible, github, Google cloud, etc. IPFS seems to be the one that people tend to use.

The metadata is a JSON file:

{
  "description": "NFT Step-By-Step",
  "external_url": "TODO",
  "image": "TODO",
  "name": "ACM",
  "attributes": [
    {
      "trait_type": "Base",
      "value": "Hash of Image"
    },
    {
      "trait_type": "Personality",
      "value": "Happy"
    }
  ]
}

The 'external_url' can point to a collection within OpenSea. You can go to https://testnets.opensea.io/collection/create and create your collection and place update 'external_url'.
Mine is https://testnets.opensea.io/collection/canoe-nft-step-by-step

The next step is first to upload the image to IPFS - then the json (once we have the URL for the image). My image via Pinata is: https://gateway.pinata.cloud/ipfs/QmPpSAxeg8mJGyvaogYfqXJpmZHMNkkvWaBFVpmHmhMzYM

Once done, the JSON looks like:

{
  "description": "NFT Step-By-Step",
  "external_url": "https://testnets.opensea.io/collection/canoe-nft-step-by-step",
  "image": "https://gateway.pinata.cloud/ipfs/QmPpSAxeg8mJGyvaogYfqXJpmZHMNkkvWaBFVpmHmhMzYM",
  "name": "ACM",
  "attributes": [
    {
      "trait_type": "Base",
      "value": "Hash of Image"
    },
    {
      "trait_type": "Personality",
      "value": "Happy"
    }
  ]
}

Now we can upload the json onto IPFS via Pinata: https://gateway.pinata.cloud/ipfs/QmTKNXG5E94FELcbNeoj55x5Ay4MvoSZb9n4n8As8KzmW7

This link is effectively what will be 'minted' or 'associated' to an address in the Solidity smart contract above.

Publish via Remix, using Metamask on Rinkeby: this is the transaction and the contract.

Next step is to link the Pinata Json metadata to an address. I will use my '0xD1eCf18C4703F524B787B9A44d7EcF58365EA74F' address to receive the NFT. Use Remix for invoking the 'awardItem' call:

The resulting transaction.

Once the call is successful, depending on how busy the network and OpenSea is, you can see the result directly on OpenSea.