Go to the Google Play Store and install by Seleuco. (Avoid "MAME4droid 0.139u1" – get the newer "M4" version for CPS-3 support)
We recommend MAME4droid for simplicity.
Google "jojoba mame rom" – common archive sites host these files. Download both jojoba.zip and cpst3.zip . jojo heritage for the future download android