To add an Item, navigate to the Project Details page for the Project that you wish to add the Item to, then scroll down to the Items section. Here, you can hover over the list to click on a "+" symbol between existing items or click the "+ Add" symbol at the end of a Phase to add an Item anywhere on the list:

After you've clicked to add an Item, a line will appear for that item, where you can choose the Item type by clicking the first section ("Task" in the image below), name the Item, and select a Start Date and Due Date. Click "Create" to save the item.

The Item Type menu will appear after clicking in to the first section of the new Item line ("Task" above). This menu is populated according to the choices made in the "Item Types" settings of your ProWorkflow account.