You can add an activity to an account or contact that is within a List. Please follow the below steps:
1. From the Navigation Panel under Lists on the left-hand side of your screen, select List Builder.
2. From within the List Builder window, click Run the on the list that you want to work with. Note: if there is no list on the page, please review this article on how to create a custom list: Monarch - Lists Builders - Adding or Editing a List
3. Check the box or boxes next to the account or contact you would like to add an activity. Then click the Mass Actions button and select Add an Activity.
4. When adding an activity to multiple accounts or contacts, you will be presented with the Add an Activity window. All activities that are added are marked with the name of the salesperson currently completing the action. Note that these activities are not eligible to be added to your calendar as an appointment. Once you have entered the activity information, click Add Activities button and all activities will be added to the selected accounts or contacts.
Keyword Search: List Builder, How to add mass Activities, Add an Activity