A second method to updating your WordPress URL when you purchase a premium domain from Hostinger or park/point your own custom domain name.
Firstly head over to 000webhost.com and log in.
Once logged in hit
“Manage Database” at top
Then select “Manage”
Then phpMyAdmin in the drop down list on your WP database
You’ll see this open in a new tab/window usually
Now SELECT your WP database on the left list
It will then display all the tables in it - you need to select
WP_OPTIONS
Once that opens you’ll see something similar to this
These top two SITE URL and HOME are the ones we want to change from yoursite.000webhostapp.com to your new custom domain newurl.com for example 
Double click on the old address and change them to the new address
Or you can click edit, and manually update them.
Enter in your custom domain in option_value once it loads replacing the old 000webhostapp.com URL completely.
Success!
Log out of your website and load it using your new custom domain - log into wp-admin and ensure everything works fine in the front and backend!
If you see to have a few broken links - permalinks might need updating - head to SETTINGS then PERMALINKS
Choose DEFAULT
Then SAVE.
Log out and try your site again.