How to set different prices to variant?

Hi, I am relatively new to Joomla. I only made up basic web sites for my own business. Now, I am trying to set up a simple store to sell our only three items (but we will sell a lot of them Until now, I tried VirtueMart until swtiching to your hikashop. What a happy change! For a novice like me, I got around much faster ans better. So thank you for your nice application.

But now I am facing a problem I just can't resolve . Maybe it is too simple. Here it is: how do I set different prices to the same item, depending on its characteristic (in this case, the duration of subscription)? From the backend of your demo site, I could figure out how to set characteristics (for different size of a man's shirt for instance). But I did not see how do I make appear a choice under the product that presents different prices the customer can click on.

I hope that I am clear enough. Thanks you in advance! Geneviève

Thank you! I did went through that, but I redid it carefully and got it through.