No prob. I use that Slot Dimension tool all the time, it's a powerful piece & relatively easy to understand if you take a minute to study the diagrams. And of course, regular practice.
Couple of hints:
-Always click the line (or point) first and the arc second. You can do the reverse but Alibre will assume the centerpoint of the arc & ignore the Slot Dimension tool (which may or may not be useful depending on what you're drawing)
-"Inside" and "Outside" refer to where the centerpoint of the curve is relative to your first reference. If the arc is closer to the line than to its own centerpoint, it's considered Inside. Choosing Outside in this case will point the dimension to a nonexistant far side of the circle that your arc would've created if it were whole (which isn't typically used, but good to know)
-When dimensioning between two arcs, the dropdown menu refers to the first thing you clicked on, followed by the second
-Also, I don't know if this was intentional, but of the 12 (!) options you're given for two arcs, you'll probably be using Center To Center, Inside Slot, and Outside Slot the most. Conveniently, Center To Center is preselected by default, Inside Slot is exactly one scroll wheel tick down, and if you buzz your scroll wheel up to the top of the list, you'll quickly find Outside Slot