With the Data Room and Unlimited Editions, you can enable the Require Agreement feature in your workspace settings. You can find the workspace settings in the top right corner of the page near the title of your workspace.
The agreement is fully customizable and will appear the first time a user enters a workspace. If the agreement is enabled after a workspace has been created, all users already invited to the workspace will have to accept the agreement the next time they access the workspace. When a user accepts the agreement, they will be allowed to enter the workspace and the Activity Log will reflect that the user has accepted the agreement. If a user declines, they will not be allowed to enter the workspace until they accept the agreement.