Here is a quick tutorial video.
To create a new product, click on the "Campaigns" tab and select "Manage products".
You'll then click on "Add product" and fill in all the product fields.
Please remember to save your work at the end.
Once the product is created, it will appear within your product list and you will need to allocate stock against it.
For more details on product inventory, check "How to manage product inventory?".