Someone explain to me how this works before I make the mistake of clicking it and using everything. Do you have to use everything at once? Does everything have to be full?

Also what is ascended and super ascended, and do I get there? An icon popped up on my phone for it, but it's no longer there.

SPs are unlocked by beating hard Ursa Luna. To use them click the checkbox on top of the powers tab.
Asc is unlocked when beating Europe Huge. You lose 100 ap and all Level progress(All Levels locked again but give full ap)
SAsc is a normal Asc but you lose all advancemants and all except 2 Artifacts. It's unlocked by spending 100k ap in phase 4. In return for your losses, you can pick one reward of the following:
-25% more ap
-another artifact to keep
-25% faster digs
-+100 start ap
These rewards stack. SAsc also unlocks a few new levels

Someone explain to me how this works before I make the mistake of clicking it and using everything. Do you have to use everything at once? Does everything have to be full?

Superpowers works by consuming 5 powers at once, but giving you the rewards of 10 powers.
This works on all powers except Multi Level.
For the time based powers it multiplies the duration by 10 (e.g. using SAC gives 50 minutes on 1 armycamp).

To use Superpowers, enable the tick box on top of the power tab.
If you enable the Superpowers without owning 5 of a power, you will get the options to buy the remaining powers with coins.

Superpowers work great on powers that instantly give result, and kinda bad on powers that are time based.
For example, you will get more armies if you use 5x normal SAC + 1x superpowered FC, compared to using 1x superpowered SAC + 1x superpowered FC.

Just wondering, once you get super power can you use it over and over, or is it one and done.

If you beat hard-ursa-luna you can use SPs untill you Super-Ascend

As stated, you can use SPs as often as you desire so long as you have 5 of that power.

However ... be careful whether you have the "Superpowers" checkbox checked or not. There are times you may only want to to use a single power (eg: if you're trying to get 2 hospital upgrades completed, you only need 2x TW twice = 4x TWs, so using 1SP TW=5 TWs but only completes 1 hospital upgrade, and to get the second, need to use another 2x TWs).

And conversely if you're trying to quicken a dig or artifact cooldown by 10 hrs or use equiv of 10 FCs, definitely use SP for each of those to get value of 10 for only 5 actual powers.