Hello I would love to know how my clients could order multiple items from my forum

You can use the Checkbox element in your form, to allow multiple selections in your form. Here's an example.

https://support.jotform.com/build/71704207494961

Is this what you wanted? If not, then let me know so that I can advise you accordingly.

Where exactly would I find the Checkbox element, when I click on the example it just shows me my forum 

On your Build section of your form, drag and drop a multiple choice element. Then under Properties > Surveying, add a value on each option of your checkbox or multiple choice element.

To compute the total of their selection, just add a form calculation widget.

The formula is simple. Just add the field of your Multiple selection element, and save your changes.

Hope that helps. Let me know if you have any other concerns.

Ok tried that but it wasn't what I was looking for exactly. Would I be able to add like a "Add to Cart" button?
Thank you for Supporting Sunnies By Nessuuhhh
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I have checked your form and I can see you have already allowed to select multiple products: 

Unfortunately, JotForm does not have a feature like an "Add to cart" button, options can be displayed as shown on the screenshot above, you are able to decide if your users can choose multiple products or only one of them. 

You may get the source code of your form in case you want to add the "Add to cart" functionality  with custom scripts , this guide will help you getting the code of your form: https://www.jotform.com/help/104-How-to-get-the-Full-Source-Code-of-your-Form 

Hope this helps.