You may want to lock down your patient manager for a number of reasons -- if you want to rely on HL7 orders to create patients, and restrict the ability to manually change or add patients to users in the Site Admin group, follow these instructions.
How to enable read-only for the Patient Manager
1. As a user with Site Admin privilege, navigate to Admin > Account
2. Make sure the top-level entity is selected. This should be the name of your organization
3. Select the "Customize" tab in the right hand pane, and click the checkbox labelled "Patients are Read Only"
If you have enabled read-only mode on the patient manager, but need to add or modify a patient, you will need to follow the same steps as above, but simply un-check the "Patients are Read Only" box in step 3.