I have an Excel-sheet where the coordinates are in meters. What is the most efficient way of inputting this file to QGIS? There are thousands of files to put so please recommend some straight-forward solution.
You save the sheet as a CSV file (Comma Separate Values format) and then import the layer as Delimited Text. In older versions of QGIS this feature was available as an installed plugin. Now it is available directly from the Layer menu.
You may also wish to try the "XY Tools" Plugin, that will let you read Excel files directly, without saving them to .csv first.