You can view your Account Custom Fields at Settings cog > Global Settings > Account Custom Fields.
Below is a basic checkbox account custom field with Mornings, Afternoons, Evenings, etc. as values.
You can import data to checkbox account custom fields by using a pipe to separate the items that you wish to import in your data spreadsheet. A pipe is a straight up-and-down line. On your keyboard, it should be located on the backslash key, usually right above or below the "return" or "enter" key. To create a pipe, hold down the shift key and the backslash key at the same time. No spaces are required before or after the pipe.
When importing this data, when you get to the mapping phase, you'll be able to map each pipe-delimited value to its appropriate value in NeonCRM.
Once you complete the import, you'll find that the checkboxes are properly populated based on the pipe delimiters in your data sheet.
In order to import multiple values to a checkbox field for existing accounts, your import data must use a different format. The import steps are the same as described above, it's only the formatting that differs.
Instead of adding a pipe delimiter between each value under a single column, you will need to place each different value in a separate column, as shown in the example below.
Neon will give you an error message if you have any duplicate headers, which is why the above example data appends (#) to the custom field name.