First I exclude the Execute portion of the fight because during the Execute phase MS will not always have the highest priority, depends on what Execute strategy people use for instance.
You just select a time by holding down the left mouse button and dragging to select an area like this:
Then right click and click "Set page to selection"
After that you go to the details page for the person you want to check.
My address field now looks like this:
You take the number in red and subtract the number in green to get total duration of the segment. In this case 250 seconds.
(You can also edit these numbers instead of selecting segment with the graph)
Take the total length and divide it by the amount of times the ability was used and you have the frequency of MS usage, OP usage and such.
To evaluate CS usage there's two things you can/want to do and it differs a bit based on spec.
For Fury you can simply take the fight length and divide that by the amount of times CS was used. This number should be as close to 20 as possible (usually more like 21 because that's evenly divisible by 1.5)
For Arms (you also want to do this for Fury) go to the "Buffs Cast" tab and click the # next to Colossus Smash in the debuff column, if you have 4t13 there will be two CS entries and you need to click it for both. One is for the proc and one is for the manual cast. Here you can see if the proc debuff was cut short by a manual CS (or the other way around so make sure you know which is which). For Arms you also want to click # next to Sudden Death in the Buffs column to see if you used the CS proc as soon as you could have. You can also see if some gaps are abnormally large here.