Hi
Select the area to copy in Excel. ctrl-c (Copy)
In Autocad ctrl-v (Paste)
If you want to create a link between excel sheet and autocad (so that when you modify the excel file the respective link in Autocad is also modified), in autocad select: Modify -> Paste Special -> Paste Link -> Excel sheet
Note: I don't have Autocad in English, so the paths might have slightly different names