That can be outstanding on our Redmine Hosting use a browser that is self-evident..
Did you also know that it is also about the smartphone but possible?
Although you could access with the browser of your smartphone to Redmine but there are more elegant and above all on display size optimized apps.
The apps are available for both Android and iOS, and available in the stores.
Always use all apps the Redmine Rest Api to access Redmine.
To activate the rest Api, navigate in the Redmine Administration in the tab "Authentication" and then enable "Enable REST web service".
Now under "My account" of the access key (user API access key) can be viewed and reset.