Adding products to issue
In order to add a product to an issue, you can do it in two ways. One way is during issue creation:
The other way is to modify the existing issue (go to all issues list, and right-click on a specific issue, the first option is Edit). Then add the product(s) in the exact same way as above.
On all issues list, you can also filter them by Product (you will find this option in the filter dropdown).
Beforehand, make sure you have the Products plugin installed and module activated.