how to link to my spaces so that files will be uploaded to spaces not the server.

If I understand you correctly, you want to upload the files programmatically to Spaces instead of the Droplet that you are using. You can use the Digital Ocean API to perform these actions, here is the reference API to upload an object (using HTTP PUT request). API exposes other functions that can be used to perform other options (delete, query, etc.).

Check this how-to guide about the Spaces API to learn about what is possible with Spaces.