For Importing the image using CSV file just provide the image name into your csv into the fields with name base_image, small_image, thumbnail_image, swatch_image
You can simply have the csv file structure something like this
SKU | product_websites | base_image | small_image | thumbnail_image | swatch_image
ABC | product_web_code | base_i.jpg | small_i.jpg | thumbnail_i.jpg | swatch_i.jpg
Images File Directory provide the path to the images something like pub/product/image or var/images
Click on the check data button for the data validation & then if everything is okay click on the import button.
Note: At the time of import Magento will look for the images from this
In the above example it can be
Magento_root/var/images/image.jpg as per your given path.
You can also provide the external link for the image download but it
is suggested to use your own server so that the downloading & copying
of file will not end up with an error of execution time out & again
produce the error as you have faced earlier.