You can Add and Item to a Project, Proposal, Invoice, or Purchase Order in DesignerLogic by using the + Add Item button at the top of the page (if it's an option you'll see it). 

This will open the Add New Item page. Some explanation:

Item #: DesignerLogic will auto-number your Items for you. If you have your own numbering system then check the 'Enter Item # Manually' button and you can enter your own Item #. 

Fill out the required fields and any spec info as well as upload a picture. 

If you know the Cost (what you'll pay for the Item) and the Markup (the % you want to markup the item) use the 'Calculate Client Price' link to fill in the Client Price (what you're client will pay for the item). 

If you know the Cost and you want to charge a specific Client Price then enter both of those and click the 'Calculate Markup' link to show what the Markup % is. 

NOTE: Markup percentages are shown as decimal numbers. For example: 50% is .5, 75% is .75, 200% is 2, etc