Where the file should be saved for this particular script is described in the lengthy post with that script, please read it carefully.
It's meant for bulk import/export of a lot of objects, so may not be the best tool for your job.
Another possible option: R80 PowerShell Module
But a simpler option is to just call the CLI directly and import the CSV.
This process isn't nearly as well documented as I thought it would be, but we're about to fix that
First of all, the CSV file should be in the correct format.
The first row refers to parameters you would pass the add host command as documented here: Check Point - Management API reference for add host
The minimum parameters needed are name and ip-address.
Since you want to put them in a group, might as well do that as they are created.
For this example, the objects will be added to a group called BlockGroup:
name,ip-address,groups.1
host1,192.0.2.1,BlockGroup
host2,192.0.2.2,BlockGroup
host3,192.0.2.3,BlockGroup
If the group doesn't already exist, you can use the following CLI command on the management server to create it first: mgmt_cli -r true add group name BlockGroup
To then import the CSV file, use the following command on the management server, which reads the file from the current directory: mgmt_cli -r true add host --batch import.csv
Note: You will probably need to break up the CSV file into smaller chunks (no more than 500 items per file).
Otherwise you may experience issues as described here: https://community.checkpoint.com/message/6809-re-creating-multiple-object-via-csv