Create macro in VBA with UserForm that pastes data selected in the userForm

I need a macro that would open an excel sheet in a background, then populates data from it and then creates a window for a user with the populated data. User then chooses the row and then clicks "Insert" button. After that, macro grabs selected data and pastes it in the correct cells in a single or multiple sheets (depending on checkbox selection).

See attached project spec with detailed description and photos.
Files for testing can be submitted upon request.