Themes in the IPS Community Suite offer an easy way to change three of the key images used by the software. They are:
The logo image shown at the top of every page of your community
The small icon shown in the user's browser tab, and next to bookmarks in their browser
The image Facebook pulls from your community when a user shares a link from your site. Often you'll use a larger version of your logo.
To change these items, edit the relevant theme by navigating to Customization -> Themes in the AdminCP, and clicking the edit icon next to the theme:
On the Logos tab, you'll see three upload fields where you can drag'n'drop your images. Click Save to apply them.
Note: The favicon needs to be a .ico icon file, not a standard image. It should also be small for best results, and is normally shown by browsers at 16 pixels by 16 pixels. Consider using a third-party tool such as this favicon editor to help.