The Lewisham actress, 20, won the part of Lola Pearce shortly after appearing on Jamie's Dream School on Channel 4.
She told TV Times: "I was more than terrified! I was really crying after we cut, because it was such a relief to get it out of the way."
Due to a long-term bladder illness, Harold only managed to acquire one GCSE during her time at secondary school.
The Walford cast member explained of her turning to acting: "Afterwards, I went straight into work and did waitressing for a couple of years, but it just wasn't what I wanted to do.
"I've always wanted to act; drama was the only lesson I enjoyed at school."
Of how she sees her character, she added: "I did have a really clear vision of how I imagined Lola to be. I didn't go to a posh school, and there were girls there like her.
"And I've tried to take bits of what I can remember of being that age - you think you know it all!"
Harold became the second soap star to act out a live birth earlier this year in a special episode to coincide with the London 2012 Olympics.