Use the with sharing keyword on the class declaration. The with sharing keyword ensures that the Apex code respects the object-level, field-level, and record-level sharing settings for the user who is running the Apex code. This means that the code will only return records that the user has access to, according to their Sharing Settings. You can find more information about the with sharing keyword in the official Salesforce documentation (https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_keywords_sharing.htm).