Don’t know if you’re going to try to use the maps api or put the data directly in the spreadsheet. If you going to go the manual path and then build a filter for WPAI.
1) Import the lng, lat and address into custom fields unrelated to ACF. This can be done in the first section of the import template
2) In the import filter, get the values from the fields you imported above get_post_meta() and build the array for ACF.
3) use update_post_meta() to insert the value into the ACF field
4) Don’t forget to use update_post_meta() to add the ACF key field. Each ACF field has a corresponding field in the database for the field key.
Even if you use the google API you’ll need to do 3 & 4
