Missing a Step in using Folder to connect to multiple csv files

I am a newbie and I am trying to read a folder to bring in multiple csv files into powerbi.  I have scowered the community, help files and youtube videos before turning to the forum to resolve an issue that is probably simple but for some reason I cant see to find documenation on.

In converting from file folder, I understand all of the steps needed except for reloading the intial combined table after the sample file has been used to create all of the transformation steps.

Here is where I am stuck:

-I connect to my folder

-I see the list of my files and choose "transform data"

-I click on the "Content" column to combine all of the files an

-I accept the default for using the First File for sample.

-Query Editor opens with the helper queris and an outputed result for the combined files

-I click on the Transform Sample File and make a series of changes that I can see in my applied steps.

-However, the default output does not change when I promote headers and this is where I am stuck.  It reflects all the changes until I get to the step where I am promoting a row to be used as headers, the default output no longer is referencing the column names as [Column 1, 2, 3, etc] and its givng me the triangle with an exlamation mark (and on apply and close I get the error message "The column 'Column1' of the table wasn't found".

I am sure its a simple reload of the final output with my applied steps, but I cant seem to find how to make this work (invoke function?  what do i put in the parameter box?).

I know its going to be a duh! moment, but I do appreciate if someone can point me in the right direction.

Thanks.