Placing Symbols in Your Project
Where to find the right symbols
Symbols are to be found in the DigiKey sidebar, to the left of Schemeit.
Let's see what inside the sections:

 DigiKey Catalog: part numbers categorized by DigiKey.
 Manufacturers: part numbers grouped by manufacturers.
 Schematic Symbols: generic electronic symbols. You can find POWER and PORT symbols there.
 Diagram Symbols: Arrows, Basic Shapes, Flow Chart, and UML Symbols.
 System Blocks: Clocks, Data Acquisition, Embedded, Interface, Linear, Logic IC, Memory,
Power, RF.
 System Icons: some common systemlevel components.
 Custom Symbols: let you draw custom symbol. (This is obsolete, use Symbol Editor instead.)
 User Library: where your favorite symbols are saved. Symbols made with Symbol Editor will
also be listed here.

Find a part number/symbol with search, the results will populate in the corresponding sections. The irrelevant sections to your search keyword will be hidden until you clear the search box.
How to place a symbol to the schematic
For symbols from DigiKey Catalog, click on a part number to show a list of available symbols. Then clicktoplace or dragtoplace the desired symbol.
If a part number does not have your expected symbol, build a symbol on your own with Symbol Editor.
For symbols in other sections, clicktoplace or dragtoplace directly from search results.