Use the constraint-based commands on the Alignment Layout Tools toolbar to add a fixed entity, a free entity, or a floating entity (lines, curves, spiral-curve-spiral groups and spirals) to the alignment.
Additional editing can be done in the Alignment Grid View:
Click the Alignment Grid View icon. The Panorama dialog will display with your alignment data.
Data in black can be edited. Data grayed out is not editable.
Click in the field to edit.
If the alignment can be modified without creating a problem, such as overlapping curves, the alignment will be updated.
Edit Alignment Data using grips:
Select the alignment in the drawing.
Click and drag grip to desired location.
NOTE: There are many grip types available to graphically edit the alignment. Reference the Civil 3D Help for an explanation of each.