Distribution companies can't get you on the radio. Traditionally, radio play is controlled by big labels with a lot of resources. Local, independent stations will often "break" new artists onto the airwaves, particularly local artists, but there are only a few of those left.
Music distribution is how music gets delivered to the listener. Traditionally, distributors enter agreements with record labels to sell to stores...
The goal of digital distribution is to get your music on iTunes, Spotify, Google Play, and other streaming platforms and digital music stores.
There are some newer, alternate ways of getting onto the radio now, even without a label backing you, but those basically rely on you finding a way to make your song a big hit BEFORE radio ever even notices you --such as viral marketing, or placement in a movie. Typically, you WILL need to be distributed to streaming services first, unless you're just relying on YouTube fame. The recent hit "Old Town Road" made it onto radio even before it was available streaming, but that's so rare that it's practically unique.
Your best bet, as an independent artist, is to build a local following of people who like your music. If you're more a songwriter than a performer, you might want to try to partner with a performer. Then, sign up with a distributor, so that people will have a way to get your song on streaming services and digital stores if they like it. Next, see if you can get it onto local radio --college stations and public broadcasting are probably your best bets. Then, make sure you have some kind of video on YouTube, even if it's nothing but audio. Obviously, the better the video the better. Finally, many of the people who have been recent viral successes have done it by somehow encouraging fun audience-participation challenges that help promote the song.