You can add, edit, show, and delete dimensions; you can also specify how dimensions appear.
Constrain panel
Dimension
Constrain panel
Dimension
In a 3D sketch, the dimension text is parallel to a plane created by the two selections.
In a 3D sketch, you can enable or disable adding dimensions to geometry as you sketch. Click Dynamic Dimension in the status bar to enable or disable the ability to add dimensions in the value box as you sketch. You can also press Ctrl + D to toggle Dynamic Dimension on or off.
Make dimensions visible so you can edit them.
Only normal dimensions can be manually edited. Convert driven dimensions to normal dimensions so you can edit them.
In an over-constrained sketch, you may have to first convert other dimensions to driven (reference) parameters, or remove some dimensions or constraints, before you can convert driven dimensions to normal dimensions.
Format panel > Driven Dimension
(2D sketches) or 3D Sketch tab
Format panel
Driven Dimension
(3D sketches) to deselect it and make the dimension or dimensions normal.