Hello Ruben
Download the installation media from SMP and start the sapinst and the stage where the installer wants the database installation it will prompt you. Most likely the ASE installation will be done using the Sybase installer.
You can check this guide for help.
Sybase ASE Developer Edition Linux Installation Guide
Additionally read the installation guide for the file system requirements.
https://websmp208.sap-ag.de/~sapidb/012002523100010937552014E
Regards
RB