Do minor changes to any theme styling, and easily display site images: logo, favicon, smartphone icon, and sharing icon.
You will need to upload all those files again, this time via the forms on the Theme Tweak Settings page. The style sheet name should still be set from before, if you used that.
For styles, only the extension (.css) matters, but it would be a good idea to name the file after the theme it overrides. For icons, they must be named exactly as shown in the Description.
The favicon.ico file is the site url image that appears in the address bar of your browser. There are free services online where you can create your own, and tutorials for making it with whatever graphics program you may have. It can't just be .png or .jpg and renamed, but must be created as an .ico file.
The phone.png image is what will appear if someone bookmarks your site via their smartphone. The size isn't critical, though roughly square is ideal, but it has to be a .png file.
The share.png image also has to be a .png file, but beyond that you can make it any shape or size. This icon is what will appear if someone shares a post from your blog on a site such as Facebook, rather than picking the first image it sees. Facebook recommends an image that is at least 200px at its minimum dimension.
The logo.png image must be a .png file as well, and like the other images, it will only appear if the file is uploaded. This one requires code added to the header.php file of your theme where you want it to appear:
<?php thtw_logo(); ?>