Your best shot at getting voice-over jobs for beginners is to sign up and create a profile at various freelancing marketplaces.
There, you can bid for voice-over projects even without prior experience, but we'd suggest, it always helps to keep a demo recording ready. The demo clip just displays your proficiency and versatility as a voice actor.
Some popular platforms you can try are Freelancer, Upwork, Fiverr, and FlexJobs.