The actor landed the role of Anthony Moon on the BBC show earlier this year and viewers will see the character's first appearance on screen next week.
In an interview with Soaplife, Lapinskas confirmed that he is "over the moon" about his new part as joining EastEnders is a "lifelong ambition".
However, asked whether he was nervous about taking on the job, he replied: "Very! As a young actor coming straight out of drama school, there's a lot of weight on your shoulders. I shot a couple of episodes of E20 before I started EastEnders so that broke me in.
"I'm lucky because Steve McFadden is my mentor and he's been showing me the ropes. He sat me down and told me all the dos and don'ts. Basically he said you have to behave and keep focused."
Lapinskas also revealed that he is planning to watch his first EastEnders episode with friends and family when it airs on Monday.
"We were going to hire out the local theatre and I invited about 100 people," he said. "But they can't get a live TV licence so it looks like I'm going to be inviting around 100 people to my house instead!"
Viewers have already been introduced to Anthony's father Eddie (David Essex) and brother Tyler (Tony Discipline).
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Watch EastEnders' Anthony and Tyler teaser video below: