Basically you need to import your comments from Wordpress into discuss. Then when you have all that working on the old site, and you import your wordpress posts into webflow, you will migrate your discus comments.
This process applies to comments only. Not importing your blog posts.
(NOTE: THERE IS A CURRENT ISSUE IMPORTING RICH TEXT FIELDS THAT HAVE IMAGE REFERENCES INSIDE - THE IMAGES WILL NOT COME OVER AND WILL BE REPLACED WITH A PLACEHOLDER)