Login to Hostinger.co.uk
Select from the menu at the top
Then you'll see your website listed as such
Click on the plus icon to the left of your domain in the list
The menu should now appear and you can select "Set Nameservers" from the list to begin.
You'll see a new menu appear with some coloured selections available select again "Nameservers"
Remove the default 4 entries and replace with the below ns01.000webhost.com and ns02.000webhost.com then select update.
Doing this correctly should result in the green tab appearing back in the main menu
Visit the 000webhost control panel and select set web address
Once loaded browse down and select add domain button near the bottom
Now I recommend using the park domain option as there isn't much left to do
Type in your domain you have purchased and select park domain
Back at the main menu waiting for nameservers should appear
After DNS updates progress through to 000webhost, your hosting will now link to your Hostinger domain!
Easy as buying the domain now upload your content and have fun creating your website!
Any questions feel free to reply!