To use flowtype with the public api of styled-components we recommend that you use the library definition in flow-typed.
To install it you can use the flow-typed cli or download it manually from the git repository and storing it in a flow-typed folder in the same folder as your flowconfig.
npm i -g flow-typed # if you do not already have flow-typed
flow-typed install styled-components@<version>
You should add this to your flowconfig if you run into flow errors from the styled-components package in node_modules.
[ignore]
.*/node_modules/styled-components/.*