You can directly assign the selected record to the User/Team.
As you click on that icon, the Assign to User or Team popup window will open to select the User/Team. [1]
After selecting User/Teams, click on the Assign button. [2]
Add Activity:
You can add the Task of selected records by clicking on Add Task icon. [3]
As you click on that icon, the Add Task popup window will open to insert the Task-related details. [4]
After clicking on Create button, Task will be added. [5]
Similarly, you can add the ‘Appointment’ of selected records by selecting the Appointment activity from the drop-down action.