As an Admin, you can select the access level separately for each report and dashboard.
Go to the reports or dashboards index screen and click on three dots on the far right side of the screen.
Click 'Settings' to go to the screen that lets you change access level.
Click on the 'Access' dropdown menu to view the list of 4 access levels.
Choose the Access level you need and click 'Save'
Public - every user in your team will have access to this report/dashboard
Users - all admins and selected users will have access to this report/dashboard.
Admin Only - only users with admin rights will see this report/dashboard
Private - only the creator of the report/dashboard will see it and only the creator of a dashboard/report can set the access level to Private.