Can I enter an activity - say a workshop I've hosted and spoken for - and then connect multiple contacts to that activity? Is this possible?

I have only three tables:  Companies, Contacts, and Activities.  I use this as a general CRM database, so I'd like to be able to not have to enter the address & related info for companies AND contacts, I'd like to be able to add one activity & then link several contacts to it, etc.  Again - I'm not tech savvy, and don't really know what I"m doing here! :-)  I didn't create this database, so I'm kinda flying blind.

From my table-to-table relationships tab:
One Activity has many Companies
Each Company has many Contacts

Does this help?