If so, please share folder structure (where is semantic path) and an example of importing a component.
I think you not suppose to get any problem to install semantic-ui inside create-react-app. This is a boilerplate not a complete rewrite, so just install it like ohter react app.
Maybe this can be easier for you. Semantic-UI for React they make this version cause a lot of vanilla semantic-ui element use jQuery. Now with this one this is only react. And for the installation just
npm install -S semantic-react and import each component you need. The link for their docs here.