Since the ToolPak is already included in most desktop versions of Excel, you don't actually need to "download" it from an external site; you simply need to it. How to Activate the Analysis ToolPak

The is a powerful built-in add-in for Microsoft Excel that simplifies complex statistical, financial, and engineering data analysis. Instead of manually typing long formulas, you can provide parameters to automated tools that generate results—often including tables and charts—in just a few clicks.

The steps to enable this feature vary depending on whether you are using a Windows PC or a Mac. Load the Analysis ToolPak in Excel - Microsoft Support