Any Excel document in XLSX format can be an XL-Connector template. To prepare an Excel spreadsheet for the Mail Merge managed package, you simply need to type in field API names into cells where you would like to see values of these fields when the Excel spreadsheet is downloaded from a record in Salesforce. You can also combine the ability to populate merge fields with XL-Connector query functionality, so that when XL-Connector Excel plug-in is installed, you can run queries based on the dynamic data. Here’s an example of such template:

Please note: while the query part gives you additional functionality of being able to pull multiple records related to the one you are downloading the template from – is absolutely optional. You don’t have to have the XL-Connector plug-in installed, you can simply use field names in your regular Excel spreadsheet, and they will still get replaced with field values.

The only important thing to remember when creating an XL-Connector template that will be used in this managed package is that before the template is downloaded from Salesforce – the managed package will go through all the cells filled with field names and replace them with the values of the corresponding field from the record the template is downloaded from.