1- Go to reflection tick all necessary module to refresh all entity and microflows
2- Create excel template or import excel from this menu to create an template
3- then write a flow and map to the button on object grid view, when press a button, will show a popup to select import file. micro flow behind should be like this
Done, you can import excel to entity that you want.
Can you give us a bit more information? What kind of columns do you have in your Excel file and how does the entity structure within Mendix look like? Also, what is the error you get?
To answer your question: it is not needed to create a microflow for every attribute, if your cell value (column header in Excel) is the same as your attribute (attribute of your entity in Mendix). However, you need to make sure your caption is spelled correctly!