"The position I'm in, I feel like I've got a lot of power," she said in a Monday phone interview with The Associated Press. "But so many kids don't feel that way. They're under their parents' rule."
Cyrus, who famously asked a homeless man to accept her Video of the Year trophy at the 2014 Video Music Awards, said she was inspired by the attention generated by that gesture. And she was further moved by the suicide of transgender teen Leelah Alcorn in December. More than 1.6 million young people are homeless in the United States, according to the National Coalition for the Homeless. Cyrus said 40 percent identify themselves as LGBT.
An entertainer since age 14, she wants to use her fame for good, calling Bruce Jenner "my hero" for shining light on transgender issues.
"When you have all eyes on you, what are you saying? And that's what I had to ask myself a lot," she said. "It's like, I know you're going to look at me more if my (breasts) are out, so look at me. And then I'm going to tell you about my foundation for an hour and totally hustle you."
Cyrus is passionate about a lot of issues, from climate change to animal welfare, but said she chose to focus on youth homelessness because it's specific and tangible.
Miley Cyrus & Zoë Kravitz Hang Out in Their Underwear in Lolawolf 'Bitch' Video
"It's something that everyone sees," she said. "It's like the birds chirping. We're consciously ignoring it at all times, but it's always happening right in front of us."
She plans to remain focused on increasing acceptance for LBGT youth and improving homeless kids' lives for at least five years before broadening her scope.
"It's not going to be an overnight process," she said. "You've got to get into a lot of people's brains and you've got to really make this a topic."
Funds raised by Happy Hippie will create digital support groups for LGBT youth and their families. The foundation is also aiding My Friend's Place, a center for homeless youth in Hollywood.
To launch the Happy Hippie Foundation and raise money and awareness for its programs, she's unveiling a collection of music video collaborations with artists such as Joan Jett and Ariana Grande. The Backyard Sessions will be available on the foundation's Facebook page beginning Tuesday.
Cyrus is also writing songs about loving one another and being true to one's self. Which comes back to why she dyed her armpit hair pink.
"The pink pits are saying, 'Don't tell me what to do,'" she said. "It's back to what I'm preaching in a way, you know, telling these kids. I'm not just saying you be yourself and I'm going to go be Miley Cyrus. I'm saying I'm going to be my (expletive) self, too."