Categories in Magento
It was frustrating setting this up and whatever I did the categories would not show on the main page.
The best thing I found was to ignore the default category and not use it, instead make your own default category. I called mine Main Products and then created subcategories (which will be the main categories of the shop) called Consumer Electronics and Outdoor Fun and Games. Subcategories of these were then made which will form the drop down menus on the front page.
Then simply ensure the shop view uses these categories.
Use the menu:
System>Manage Stores>Store name
then select Main Menu as the categories.
Fairly simple in the end but took a lot of patience to get there. Another Magento user unfriendly feature.
Next task is to copy and paste the CSV from ZenCart products to product numbers.
It should be straightforward to find and replace the old category name with the new category number. In Magento simply click on the category in the admin menu and it shows the ID number at the top of the edit page.
Images.
Magento appears to handle images well so I am not going to use thumbnails or different sizes but only one image and let Magento handle resizing.
They can be copied over from ZenCart quite easily using the information from v_products_image. You probably have something like a products directory and imagename.jpg so your CSV file looks like products/imagename.jpg
Copy the complete image directory with all your image files to /media/import/
Mine is therefore media/import/products/. Copy and paste the Zencart CSV column to the Magento CSV column called image. In the Magento CSV column the directory name needs to start with / so simply do a find and replace on the whole column. I did find products/ and replace with /products/. If you use the Zencart small medium and large image sizes you will also need to find and replace .jpg with _LRG.jpg otherise you are almost done.
small_image copy and paste column from image
thumbnail copy and paste column from image.
Thats it!