Insight Timer is a free app that has 24,000 free guided meditations and the number grows every day. This app allows you to set a timer with bells and ambient sounds or choose your favorite type of guided meditation with the help of topics, filters, and ratings. There are courses (the only part that costs money) but other than that there are no annoying ads. Your therapist can help guide you to meditations that would be best for your specific situations and mindset.
Calm gives therapists a free year and their clients 30 days free. It has a lot less content but can be simpler to use. If you are interested, ask your therapist for the handout with 30 days free.