So we have an existing website with a Modx Framework and with this updated website, we will be using Wordpress. We have already downloaded the template that we want to use, I don't know what to do next.

Do we still need to access the Modx manager or do we just create a new Wordpress account? We have no intentions of using any content from the existing website, it is going to be from scratch.

If it is going to be scratch, just create the new website with wordpress and then put it on your hosting server removing the old one.
That is it.