Hi Wayne,
You can import activities into Method using the Import / Export tool. I suggest you head over to Customize > Tables / Fields, take note of the required fields and export your Activity table to study the field formats first. Then, when you’re ready, use your customer list to fill out the contact for your activities (keep in mind, activities are linked to contacts, not customers) and do the rest of the entry in Excel.
I hope this helps.
-Audisho