As a Code Exchange user you can raise issues or provide feedback to the project members of a project without being a member of that project.
To do that simly open the "Issues" tab of the project and check whether or not that issue has already been raised. You should avoid creating issues that are already taken care of.
If the issue hasn't been raised, yet, click on the "Create issue" action link.
Now you can add what kind of issue you see. The short text should describe briefly what the issue is. In the field "Issue type" you can tell the project members if you think you have encountered a bug (select "bug" as issue type), if you have a feature request (select "Enhancement") or if you see any other kind of issue (select "Other" as issue type).
You should keep the "Priority" at status "Normal" as long as you feel that your issue either deserves more ("High" or "Highest" priority") or less ("Low" or "Lowest" priority) attention by the project members. The project members might change the priority from what they feel is the best match to their current planning.
In the description field you should try to describe the issue in a way that the project members can understand what your point is. There is no need to write a novel here :-), but try to be precise.
After providing all the details just click on "Submit" and that's it. The project members will now look into the issue and will try to address it.
Please remember that the project members normally are providing this service in their free time and don't have a professional support team to handle all the incoming issues. Therefore please be patient.
You can follow the status of your issue by checking the "Status" field of the issue in the list of issues. Once your issue has been fixed the status is set to "Fixed".
But you can also comment on other issues. Just click on one of the issues and click on the "Add comment" link. You can now comment on the issue and e.g. support the issue or add some additional related ideas to it.
Hope this helps you to understand how the issues management works in Code Exchange.