1. Go to Setup > Fields.
   
2. Click the icon next to the module or the More icon.
   
   
3. Select the Default Access Level and configure the desired access level, such as Private, Public Read Only, or others.
   
4. Once the settings are configured, save the changes.
   

Types of Accesses 

• Private: Ensures that only the record owner and admins can view the records.  
• Public view only: Allows peers to view records without editing them.
• Public view and edit: Public view and edit enables peers to view and edit records,
• Unrestricted: Full access, including the ability to delete records.
  
  

Notification  for the changes

Notes:

• All record-level permissions are managed through the Default Access Level feature, while actions at the related list level, such as activities, are configured using Profile Permissions. For example, if a user has permission to create activities, they can still add activities to a record's related list, even if the Default Access Leve​​​​​l feature grants them view-only access to the record.
• If peers with access to your record make changes like edits or deletions, they cannot be undone.