You must be logged in to your page to update your fitness manually.
If you want to add miles to your page manually, click the fitness icon in the bottom of your "post an update" text field.
An interactive status will display. Each of the coloured sections can be edited to reflect a ride, run, walk or swim and you can easily add your distance, duration and time of day to your post.
Click "Post" when you are ready and then refresh your page. Your workout will now appear in your feed.