This repository was a storage point for much older SIGCHI templates which have long since been deprecated.
If your conference is using The ACM Publishing System (TAPS), please see this article which outlines the workflow and templates. This includes best practices and accessibility requirements.
There is a chance where you may be using an interm Word template. The ACM has details on the Master Article Template page.
As always, please refer to the _specific instructions from your conference's call for papers_ and submissions.