Add your own logo

Replace the image and the name in the sidebar's .sb-brand block, and the favicon.

The logo sits at the top of the sidebar, in .sb-brand:

<a href="index.html" class="sb-brand">
  <div class="logo"><img src="images/favicon-white.svg" alt=""></div>
  <span>ODIN <span class="brand-dot">ADMIN</span></span>
</a>

Put your logo in images/ — an SVG stays sharp at every size. The sidebar is dark, so use a light version.
Change the src of the image and replace the name. .brand-dot colours part of the name in the primary colour; leave it out for a one-colour name.
Replace the favicon link in the page head with your own icon.

The sign-in and register pages show the logo too — update them the same way.