You can contact a prisoner by writing to them. Normally there’s no limit on the number of letters you can send.
Most letters sent to (and from) prison are checked by prison staff.
Letters from solicitors and courts must not be opened, except in specific cases (eg where there’s a suspicion it’s not from a legal adviser).
You can complain to the prison if you think your letters are being read when they shouldn’t be, or if your letters aren’t reaching the prisoner.
The prisoner has to call you using a prison phone.
Prison staff can listen to most types of call and they can be recorded, but some calls are not monitored or recorded - eg to the prisoner’s legal adviser.