Lets assume, you have all your static files in the /public folder of you app. Generally spoken, if you are using express.static, you should also get your index.html because this is handled by default for each directory.
In your case, as you are using Angular, the routing is handled from the client side (SPA). You should only have one single index.html after building your Angular app. All files from your dist folder should then be placed into your /public folder. Then you need to make sure, that initial file serving provides your index.html like so:
In this example static files are served first, then your API and if nothing is found, you are getting back you index file.
const express = require('express');
const app = express();
// serve static files
app.static(__dirname + '/public'));
// serve your API
app.get('/api/welcome', function (req, res) {
res.send('Welcome');
});
// fallback routing (server side handling)
app.get(/.*/, function (req, res) {
res.sendFile(__dirname + ‘/public/index.html‘
});
app.listen(3000);
Next time please make sure, to give all necessary information in your question ;-)