Spiritually, when we recognize that something – payments perhaps, or information – is occurring in instalments we must understand that what is represented must happen, or occur to us, gradually. Perhaps we need to learn in bite-sized chunks.
Psychological / emotional perspective: In dreaming of instalments, from an emotional perspective we must accept that there is a degree of conditional acceptance, either in ourselves or others. We may not be ready to make a full commitment.
Material aspects: To install something is to put it into position.
A new programme on a computer in dreams would, for instance, mean accepting a new way of working.
A new instalment of a story suggests a different phase in a project.