The only command security permission needed for the "Open in Excel" command is View Issues (or View Test Cases or View Requirements). You need to have Excel installed on the computer. You also need to select 1+ issue from the list window for the command to be enabled, as Helix ALM will be exporting only the selected items to Excel.
Helix ALM does not have an "Import from Excel" command, but it does have a "Text File Import" command. If you save your Excel file to a comma delimited or tab delimited file, then you can import that file into Helix ALM.