When viewing a candidate, you have the ability to add or update the resume they have on file with you.
Click a candidate's name on an interview card to be taken to their profile.
On their candidate profile, select Actions > View/edit resume
If you don't currently have a resume on file for the candidate, you'd simply select a file to upload or drag and drop it in the uploader. The resume will appear once it's done processing.
If you already have a resume on file for the candidate, click Reupload to overwrite the file and you'll be presented with an option to select the file you want to upload. Since you're overwriting the file, we recommend downloading the existing file before uploading a new one.