Step 1: Login To Plesk Control Panel.
Step 2: Go to Files.
Step 3: locate the file or directory for which you want to set access permissions, then click the arrow in the corresponding row,
Then Click Change Permissions in the drop-down menu.
Step 4: Click on the appropriate User from left e.g. (Application pool group (IWPG_example1) next adjust the permissions as required on the right.
Step 5: Click Ok to save.