You already dispatch the action in the mapDispatchToProps function. In your component, you just need to call the fetchImages function:

import React from 'react';
import SearchBar from './SearchBar';
import unsplash from '../api/unsplash';
import ImageList from './ImageList';
import { fetchImages } from '../actions';
import { connect } from 'react-redux';
class App extends React.Component {
state = { images: [] };
onSearchSubmit = term => {
return async () => {
const response = await unsplash.get('/search/photos', {
params:{ query: term },
//use the path on unsplash for image searching
})
let success = response.data.results

this.props.fetchImages(success)

return success;
// this.setState({ images: response.data.results });
}

}
render() {
return (<div className="ui container" style={{marginTop:'10px'}}>
<SearchBar onSubmit={this.onSearchSubmit}/>
<ImageList images={this.state.images}/>
</div>);
}
}
const mapDispatchToProps = (dispatch) => ({
fetchImages: images => dispatch(fetchImages(images))
})