There are two ways you can add an activity (Call, Appointment or Task) in BuddyCRM. The first is by clicking on the Plus icon in the top right of the screen.
This will bring up the following view. Select the activity you wish to create by clicking the relevant tab along the top.
Fill in the details and select Save. In this case, the call will be saved against your selected lead or account and will appear in your calendar for the date you select.
An alternative way that you can add an activity in BuddyCRM is to select Calendar, and click on the day you wish to add the activity for. A pop-up will appear as shown below, select which type of activity you wish to add, and as before simply fill in the activity details and select Save.