Sorry that you cannot add presets in Lightroom CC. Please refer the below steps to install presets in Lightroom mobile:
Install Lightroom CC on your desktop.
Launch Lightroom CC desktop. When you launch Lightroom CC desktop (v1.4 June 2018 release or later) for the first time after installing or updating, the existing Lightroom Classic profiles and presets on your computer are automatically migrated to Lightroom CC.
(Optional) If you make any changes or add new presets to Lightroom Classic (after auto-migration to Lightroom CC desktop), do one of the following:a. Migrate the new/updated presets to Lightroom CC manuallyFor Help instructions, see Migrate Presets.b. Use the import dialog in Lightroom CC desktop
From the menu bar, choose File > Import Profiles & Presets.