To enable Requests, select All Workspaces from the drop-down list in the top navigation. Click the Settings link at the top of the page. On the left menu, under Global Settings, click Features to display. Click the checkbox next to Requests under the ENABLED FEATURES column. This will enable the Requests feature for all workspaces.
You can hide Requests by unclicking the checkbox next to Requests. Requests also can be enabled/disabled for a specific workspace under Settings for that workspace.
By default, Reviewer and Partner users cannot view the Requests feature. To enable access, click the check box in the Reviewer or Partner column on the Requests row.