Under certain circumstances, it may be easier to prepare your data in another spreadsheet, such as Excel, and then paste them into the Data Editor. This is a likely case when new data has been taken and needs to be appended to the existing information. In this case, first copy the data from the external application. Then click in the (new) row at the appropriate place and type CTRL+V (or right mouse click and select Paste). Note that when Automatic Error Checking is on, you may see some red cells after you click in the (new) row. This is normal, and you should go ahead and complete the paste.
If you want to paste revised data over existing values, first copy the values in the external application. Next, select the appropriate cell where pasting should begin. Type CTLR+V (or right mouse click and select Paste).
For more information, see Data Editor.