1. From Setup, enter Profiles in the Quick Find box, then select Profiles.
2. Select a profile and click its name.
3. In the Apex Class Access page or related list, click Edit.
4. Select the Apex classes that you want to enable from the Available Apex Classes list and click Add. Or select the Apex classes that you want to disable from the Enabled Apex Classes list and click Remove.
5. Click Save.