If by "aligning" you mean make the leaders line up with each other, you could try moving them around and any dimensions which share a leader will snap to each other. What I do is create snap lines, then move the dimensions onto the lines, etc.
As Don suggested you can use Align dimensions from Annotate group OR select dimensions > Right Click > Align dimensions
You can also add snap lines around a view - this is my preferred way of working. These allow you to arrange your dimensions evenly, but do not show when you print the drawing.
Typically I set the first line 15 mm from the view boundary, and space the lines at 12 mm intervals. I generally create more lines than I think I will need (usually 6 in one location, but maybe up to 10 for a complex part or as few as 3 for a small detail view).
You can also select the dimensions, then right-click and select "Clean-up Dimensions".
This will launch the tool to create snap-lines which align the dimensions.