Software Deployment

I need to create an update package which would include the previous version of the application currently installed on the system but i am confused about the update process since there exist an old msi and updated msp already on the system?

In the past i would only provide old msi for the update but since there is msp should i just include msp only and msp? I guess msp should already contain update info for the old msi correct?

Do i just include MSP in the update tab in Wise Package Studio?

Thanks,
XaviorPL