Once you have Zencart installed and operational, you can load the Easy Populate (EP) module via FTP to your server.
The EP module files are available HERE
Simply UNZIP the module on your local drive. When it's unzipped, look in the directory where you unzipped it and you will see TWO yellow folder icons:-
admin
temp
... followed by a few files.
Ignore those FILES for now - focus on the two folder icons.
Open your FTP program.
In the left pane of your FTP program, navigate to the EP directory on your local drive, so that you see the admin and temp folder icons (and those files I spoke about).
In the right pane of your FTP program, link to your server, and navigate to the directory where you have your main ZC folders.
You will know you are in the right place when you see (amongst all your other ZC folders) the admin folder.
Now you are at the correct directory LEVEL to upload the EP module.
In the left pane, select BOTH the admin and the temp folders.
Then, after making sure your FTP file load protocol is set to AUTO (or ascii), click the FTP arrow that sends these folders from your local drive to the server.
Then, login to your shop admin panel and look under tools menu.
Open EasyPopulate and proceed according to the instructions that accompany the EP module (the readme files).
To see how EP works, go to the WIKI on this site, and search for Easy Populate.
Schoolboy has written a good tutorial on how to use EP.