If you'd like to highlight contract terms for future reference, just navigate to the contract and select the text you want to highlight. You will see the text highlighted in yellow along with a menu of options available (See below). 
If you would like to remove the highlighting, you can click the highlighted text and select "Remove Highlight" from the menu of options.
Note:
A highlighted text gets increasingly darker as more highlights are placed over it. Texts can have more than one highlight and highlights can overlap.
This feature requires that Annotations are enabled for your account. If you don't have the option to highlight text, please see one of your ContractSafe Admin users and ask then to enable Annotations for your account in Settings > AI and Workflow Options.