Check out example codes for "download button html". It will help you in understanding the concepts better.

Code Example 1

<a href="the/name/of/your/file.x" download>

Code Example 2

<!-- Add icon library -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">

  
<!-- Auto width -->
<button class="btn"><i class="fa fa-download"></i> Download</button>

  
<!-- Full width -->
<button class="btn" 
  style="width:100%"><i class="fa fa-download"></i> Download</button>

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