You have two primary options for planning a funeral even though a person wishes to be cremated.
1) You can have a traditional service (visitation with the casket present) prior to the cremation taking place. This type of service may require embalming and is usually held at the funeral home or a church.
2) You can have a memorial service (no casket present, but perhaps the urn on display) immediately following the cremation or at a later time if it is more convenient for out-of-town family to have the service a few weeks later. This type of service can be held anywhere that accommodates the number of people you expect to attend.
You can really design any funeral service you feel would best honor the deceased. The main issue is whether you want the body present (prior to cremation) for the service you plan.