When setting up the details of the Internal Check, if you set a user to complete a check and select a person(s), you will be able to create a schedule.  A schedule window will appear here. 

Step 1: Select Schedule 

Step 2: Select which Frequency Set the required settings for your schedule then select Generate Schedule

Step 3: The schedule will look like this below from here you can edit and Save 

Step 4: At any stage if you need to re-edit go back to check, select Edit Details

Step 5: Then select Schedule 

Step 6: This page will open where you can Edit, Extend or Delete