By sample databases I'm assuming you mean the pubs2 and pubs3 databases. If this is the case then yes you should be able to create them manually as long as the files were installed with your software.
cd ${SYBASE}/ASE-15_0/scripts
You're looking for a couple files that are named installpubs* (or instbps* on Windows).
Keep in mind that you'll first need an operational dataserver configured and running. Then you run one of the installpubs* scripts against the dataserver (eg, isql -S <server_name> -U <login_name> -P <password> -i installpubs2).
On a plain vanilla, just out of the box, dataserver the pubs* databases will be created on the master device. If you want to install the databases on a different device you'll want to make a copy of the installpubs* file, then edit the copy to fit your situation (eg, get rid of the drop/create database commands if you've already created an empty pubs2/3 database; modify the create database command to run against something other than the default/master device; etc).