To begin with adding your product's attributes, we have to first add them to your attributes. So we begin by going to "Manage Attributes" in the "My Store" dropdown or on the home of your seller area. Below is an image of the home with the dropdown showing where to go.
Once we've reached the Attributes, which should look like the image below, we click the green plus button(shown below in a red circle) to add in a new attribute to our area.
Once you are at the edit/add attribute screen(example below) you will want to name your attribute appropriately for your product and so customers will know what it is. If possible, add the attribute to an attribute group for customers to be able to search for. However, be sure that the attribute should belong to a group before you add it to that group. Don't for get to save by clicking the floppy disk save at the top of the area, like in the top right of the image below.
Now that you have some attribute(s) set up, it's time to add them to your product(s). While adding your products, you can select the "Attribute" tab, which should look like the screen below, and then click on the green plus to add your attribute(s) to the product you're adding.
After clicking the plus, you should see an Attribute area(circled in red) and a Text area(circled in blue) like below. If you begin typing in the name of your attribute you made before, it will show in a dropdown that you can select it from in the Attribute area. The Text area is for you to add the description for your Attribute, like for a processor attribute you would put what processor your product has in it.