You can't currently log one outfit with both pants/leggings and a dress/skirt (yet! We'll likely add this feature down the road). However, it is still possible to add all those items to outfits on your home page so your log information is correct. Here's how you can do that: log your first outfit with the pants/leggings, then log a second outfit with just the dress/skirt. You can read more about logging multiple outfits here: https://cladwell.zendesk.com/hc/en-us/articles/360006307673-How-do-I-log-multiple-outfits-per-day-.
Alternatively, you can create an item that is a dress, but tagged as a top. This would result in the dress being paired with pants automatically within the app!