The JLS star popped the question during his New Year break with Wiseman, one-fifth of girl group The Saturdays.
However, speaking to Hello magazine, the 26-year-old revealed: "I can't tell you how many times I'd rehearsed what to say, but when the moment came to speak it all went to pieces - the only time I've ever messed my words up!
"I was stuttering and stumbling. I said to Rochelle, 'I want to make you the happiest man… No, I mean I want you to make me the happiest man'. It was getting all confused."
Wiseman admitted that she was unable to stop looking at her heart-shaped diamond ring, telling the magazine: "I kept waking up, gazing at my ring and thinking, 'Yes!' After a couple of days Marvin did have to say to me, 'Babe, you've got to stop looking at it!'"
© Rex Features / Copetti/Photofab/Rex Features
© Rex Features / McPix Ltd
Humes added: "From the moment I slipped that engagement ring on Rochelle's finger I've felt a tighter bond with her. I assume marriage will make that closeness even greater."
With a summer wedding planned, Wiseman said that she would have her uncle, former England captain Paul Ince, give her away on the day: "My dad has never been around and it's Paul who will give me away at my wedding."
Both confirmed that they have asked their respective bandmates to serve as bridesmaids and ushers.
The full interview appears in the new issue of Hello magazine, out now.
> JLS Marvin Humes: 'Rochelle Wiseman wedding will be massive'
> The Saturdays meet US TV executives for new reality show
