Have you installed younity on all of your computers (Mac and/or Windows)?  You must install younity on your computers and register them for their files to be unified and streamed via younity to your mobile devices.

When you open younity, does an "Updating file metadata" message appear? If so, younity is still pulling in the data from your computers. 

If it seems to be taking a very long time to pull in the data, you may want to limit the number of files to start.

By default younity will scan your entire computer. This may take anywhere from a few minutes to several hours depending on how many files you have and how new/fast your computer is. If you want to get started more quickly, you can limit the files being scanned by following these instructions.