It is great news that you are resigning.
It is very easy.
Just email email@example.com
Name, date of birth, membership numbers.
Just state these in the email.
Just say you are resigning with immediate effect. You may be contacted or not, it will depend upon your country and Stake. The standard time for resignation to be processed is around 6 weeks. After this time, try to log into your LDS account if you have one, or set one up on Family Search. If it does not allow you, then you know admin have done their stuff. Important this because it gives you confirmation without hassle of speaking to local leadership/ membership records.
No need to give any reasons in your email. This is not therapy, this is an admin transaction.
Sometimes a bit of fine tuning is needed along the way because of awkward personnel/ circumstances but deal with them as they arise.
My mother had her membership resignation processed in 2 weeks from me sending the email.