I haven't tried redemptions as I don't have enough miles to redeem flights (for flights where I earn enough miles for redemptions, I put all of that on DL), but redemptions seem easy: you have the option to book flights with miles as you book them, so long as you're logged into your Suma account and are booking with UX.

For all other flights you will need to call. I speak Spanish so I expect the process to be fairly smooth for me, but I can't say the same for you.