Your app logic seems fairly simple. Lets break your question into 2 parts:
1. How to achieve app requirements
Start with basic Express on Node. Create the route for the login page at
http://mywebsite.com/admin
like this:
app.get('/admin', function(req, res) {
// Render login form
});
Now you need to validate the username password from the form, and accordingly redirect the user to login failure or success page (or your "Add a product" page). If you are routing the user to the product addition page, make sure you use some middleware like Passport so that only an authenticated user can view that page.
app.get('/product/add', isAuthenticated, function(req, res) {
// Render product addition form
});
This add a product page can have the form with all your requirements. Since Express 4.x has dropped built in middleware for multipart form data (used for file uploads), you will have to use Multer or an alternative.
app.post('/product', multerInstance.array(), function(req, res) {
// Get post data from the form at /product/add
});
Your "products" table/collection should auto-assign an ID to every product added.
Now you need to create the route for the product display page. You could have a route like "/product/:id" and handle the id param, so that "mywebsite.com/product/id1" shows data for product with id "id1".
app.get('/product/:id', function(req, res) {
var id = req.params.id;
// Render product page based on id
});
This is the most crude way to make your app. Please consider reading up more about express, routes etc before putting this into a production environment.
2. Hosting on AWS
Your app would typically be hosted on port 3000. AWS provides extensive solutions for domain name resolution, load balancers and port forwarding.
First create your EC2 instance and point an Elastic Load Balancer (ELB) to it. Your Node app is on port 3000 but you want to expose it via port 80 on your domain name. Your ELB can take care of the port forwarding. Add listeners like this :

Now point the A record of your domain to this ELB (A record will be of "alias" type on Route53):

Thats it! You have now deployed your app on AWS!
Extra You can use nginx on your EC2 for port configuration, cache control and additional power ups :)