Questions about covaraites in group-level statistical analysis

Dear Experts

Here is a couple of questions regarding a covariate analysis for rsfMRI:

1. For motion regreseed (as Text Covariates) -> choose mean FD value in headmotion.tsv under the the directory of Realignment right?
2. For global iFC correlation (as Covariate images)-> which files should I pick up? (FC_FunImgARglobalCWF?)
3. Gray matter portion (as Covaraite images) ->choose wc*.
4. Any suggested reading or example for ANCOVA and repeat measure setup

Thanks for considering my request!

Cheers

Larry