Step one head over to Freenom.com and login to your account
Go to “My Domains” select Manage Domain
https://my.freenom.com/clientarea.php?action=domains
Under Management Tools select URL Forwarding
Type in your 000webhostapp.com domain
Ensure you get this message
If you get any issues select Manage Freenom DNS then select use default (Freenom nameservers)
Then try making the URL forward again.
https://my.freenom.com/knowledgebase.php?action=displayarticle&id=5
Now when you visit your custom domain you’ll see your 000webhostapp hosted content.