Practice makes perfect.
Practice sessions develop and build on existing skills. Match play is where those skills will be demonstrated. Quality practice induces and requires high levels of concentration. This will flow on into match performance. Focus attention on developing sound routines until they become automatic.
May I recommend the following 7 minute video. It features Jo Edwards and Shannon McIlroy demonstrating the basic bowling technique – grip, preshot routine, standing on the mat, delivery and follow through. It is well worth viewing multiple times.