No matter how you choose to get the files, make sure that Popper is include before the picker's main script file.
You will also want a font library. The picker defaults to Font Awesome 6, but you can provide a different icon set via the configuration or a plugin.
<!-- Popperjs -->
<script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.11.6/dist/umd/popper.min.js" crossorigin="anonymous"></script>
<!-- Tempus Dominus JavaScript -->
<script src="https://cdn.jsdelivr.net/npm/@eonasdan/tempus-dominus@6.4.4/dist/js/tempus-dominus.min.js" crossorigin="anonymous"></script>
<!-- Tempus Dominus Styles -->
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@eonasdan/tempus-dominus@6.4.4/dist/css/tempus-dominus.min.css" crossorigin="anonymous">
npm install @popperjs/core @eonasdan/tempus-dominus
You can grab the compiled js and css from GitHub
You still need to get Popper yourself.
Install-Package TempusDominus
#or the SCSS version if you prefer
Install-Package TempusDominus.scss