Follow below steps to create a filter:
1. Login to your Gmail Account.
2. Tap on the Settings icon in the top right corner and choose Settings option in the drop-down menu that appears.
3. Tap on the Filters and Blocked Addresses tab.
4. Click on Create a New Filter button.
5. In the window that pops up, type the email address you want to whitelist in the From field.
6. You can adjust any of the other options for a more specific filter of your choice and then, go ahead and click the link called Create filter with this search, which opens an options screen.
7. Place a check in the box next to Never send it to Spam and other options of your choice.
8. Click Create a filter to save the changes.
9. You can now see your filter under Filters and Blocked Addresses.