Setting the Publish Date to Match the Social Media Post Date
If you click "Create Post" or "Import All Checked Rows" with the Post Status set to Publish, then the publish date will match the social media post date.
However, if the Post Status is set to Draft and then you publish it later, WordPress will set the publish date to the current time of publishing it. If you are in the list of Posts and click on Quick Edit, you can change the Status to Publish, but you can also change the date there. Unfortunately, it defaults to the current time, and you have 5 date and time fields to change. The same thing happens when you open the post for editing and then click Publish. Click the dropdown menu "Publish: Immediately", and it will open up the 6 date and time fields to change there.
Changing 5 to 6 date and time fields is very tedious. It is recommended that you set the Post Status to Draft when you are practicing, and then delete those posts when you are finished. When you are familiar with the options and have a plan for how you want to group posts and limit by date periods, set the Post Status to Publish and then click "Import All Checked Rows". All of those posts will have the appropriate publish date and time.