How do i get predicted grades if im doing A levels online?

It’s not predicted grades that are most important (many applicants apply without predicted grades).

You need an academic reference for a UCAS application. It’s up to you to find someone suitable willing to provide you with a reference.

Whoever provides your reference will have the option to provide predicted grades. It’s up to you to negotiate with them to find out if they’re willing to provide predicted grades in their reference and if so what evidence and information they need to reassure them that the predictions are sound.