Activities can be used to track interactions that you've had with a client, and can also be used to easily set reminders and tasks for yourself. The easiest way to create a new Activity is from the Global ADD button from the top-right of your screen.
When clicking the Global +ADD icon simply choose Activity to create a new one.
This will bring up the "Add an Activity" pop-up, as shown below.
Use the left column to choose your Activity type, set the qualifications for it.
The right column should be used to ensure this Activity is filed against the appropriate Contacts, Accounts, Agencies, and even Deals if there's one in the system associated with this Account already.
Use the Notes field to enter any details you want to easily be able to recall regarding this task.
Don't forget about Matrix Mobile!
You can also easily add Activities via your smartphone. Simply open up Matrix Mobile, and you can create a new Activity by clicking the Actions button on the bottom right.
The Activity form offers the same fields on your phone, but it's now more streamlined so you can easily scroll.
Keep in mind that your phone's Voice to Text functionality will work perfectly within Matrix Mobile, so you can use that to easily talk you notes from an Activity into your phone while you're walking out of a meeting.