Alright, first things first. You gotta set up Firestore in your Firebase Console. Add Firebase to your Android or iOS app and get Firestore up and running. Oh, and don't forget to include the GeoFirestore library in your project. This nifty tool helps you filter documents based on geographic radius.

Now, for storing geospatial data, you'll need to save the location as a GeoPoint, which is basically latitude and longitude. Use the GeoFirestore library to set this up. Here's a quick example:

const geofirestore = require('geofirestore').initializeApp(firestore);
const geoCollection = geofirestore.collection('collection_name');
geoCollection.add({
   coordinates: new firebase.firestore.GeoPoint(52.52, 13.40),  //Latitude and longitude
   /* your other data fields go here */
});

This code creates a document in your Firestore under the collection named 'collection_name', with a 'coordinates' field containing the geographic location.

To fetch results within a certain radius from a geographic point, use the query feature of GeoFirestore. The results will be sorted from nearest to farthest.

const query = geoCollection.near({
   center: new firebase.firestore.GeoPoint(52.52, 13.40),  // Center around which to search
   radius: 10   // Search within a radius of 10 km
});
query.get().then((value) => {
   console.log(value.docs);  // All matched documents with 'coordinates' within 10 km of the center
});

This will give you all documents within 10 km from the specified center point.

Updating geospatial data is pretty similar to updating any regular data in Firestore. But, make sure to use GeoFirestore's set or update method to keep the GeoFire data consistent.

geoCollection.doc(doc_id).update({
   coordinates: new firebase.firestore.GeoPoint(52.22, 14.45),  //New latitude and longitude
   /* your other data fields go here */
});

This updates the 'coordinates' of a specific document identified by 'doc_id' in your Firestore collection.

Deleting geospatial data is just like deleting regular Firestore data. Use the delete method associated with the document reference:

geoCollection.doc(doc_id).delete();

This will remove the document identified by 'doc_id' from your Firestore collection.

Remember to handle errors and edge cases in your implementation. This guide assumes you have a general understanding of Google Firebase Firestore and how to use it in applications.