If should be fine to use since most of the gas station in the US use at least 10% Ethanol. Read the instruction on the bottle, you should use it with an almost empty tank (1/4 or less). 

If you want to use the cleaner @yaser 's advice is right. No matter what the label says, use it at 1/4 tank and go near empty before you "gas up" again.

People use these cleaners all the time and it's usually out of desperation. But it can't be ignored that sometimes they work.

However, I'm a big fan of "if it ain't broke, don't try to fix it".

So, are you entertaining the thought as a "preventative measure" or do you suspect that you have a clogged injector?

These cleaners are combustible solvents.

So are Gasoline and Ethanol.

The difference is that the cleaners are stronger combustible solvents.

So, they'll break loose crud that the gasoline and ethanol won't.

You're going to add it to your gas tank so any crud between the gas tank's filter and the fuel injectors will be "loosened" and pushed through the fuel injectors. (who likes the sound or that?)

If you really need to do this there's a better way. 

Scotty did a video on these Gizmos years ago, back when he had more hair than forehead.

But the Injector cleaner kits are still available. Your issue would be that you probably don't have a schrader valve on your injector rail on that Ford Focus.

You'd probably have to install a T-fitting. 

It would be worth your time if you suspect a clogged injector. Not so much as a "preventative measure"

As an aside, I have 2 vehicles pushing 200,000 miles. I've never added fuel injector cleaner or replaced any fuel injectors on either of them.

https://youtu.be/bKGI9N_yWd0?t=30