Typically you do this using Import/Export rules and a data connector. If you want to match data to a device you will need to use a Key i.e. Server Name.
Create the data classes and resource associations before hand and always start with a small subset of your data, invariably there is an element of trial and error in matching data from different sources. Also remember the golden rule of CMDB management "Adding information is easy removing it is hard".
In the ideal world you should be trying to get the information from the assets, managing a spreadsheet requires just that Management, consider what you are importing and if automation is possible.
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