I tried to find myself, but there is a bit more detail on the help site which isn't very well linked to: http://help.micro.blog
A specific example is given on the IFTTT [2] page, but I am unsure if that is the best way to achieve RSS cross postings on micro.blog.
> "If you already have a blog, such as one based on WordPress, connect it to Micro.blog by adding the feed URL to your account under Account → “Edit Feeds”."