Cmsmasters' themes allow you set two types of icons via theme general settings, which are Heading Icons and Social Icons. Heading icons are used for custom page headings and also in some other website parts, like in Featured Block Widget etc. Social Icons are mostly used in Header and/or Footer for social sharing.
To add an icon you should follow to Theme settings > Icons:
1. Heading Icons
Choose, for instance, heading icons tab and click "Add new icon":
Add an icon from the URL or your computer and click "Choose" to add it to your menu:
Your Icon will appear in the Icons area. Save the changes:
2. Social Icons
Follow the similar procedure for Social Icons:
When your Social Icon is added to the Icons are, you will be able to add a link to it, add hover color (in some themes) etc.