As a peer-reviewer, your job is not to make changes or edits to the manuscript you are reviewing. Thus, there is no option for reviewers to upload a manuscript with tracked changes. Rather, you are asked to supply a numbered list of issues, which you can copy & paste into the review form (see What does the JMIR Review Form look like?).
Note that reviewers are not expected to correct language issues, typos, etc. These issues will be addressed by the copy editor during the production stage. You are asked to comment on the academic content, clinical relevance, methodology, validity of statements, and completeness of references/related work being cited. Please read our instructions for reviewers.