It depends on the text file. If you got it as an output for an experiment, you should be sure to save it as a CSV, or Comma-Separated Value file. Then you can load it into Excel 2010+ like so:
- Click the Data tab.
- Under "External Data Sources", click "Text".
- Locate your text file and choose it.
- Click Next.
- Click "Comma", or any of the radio buttons so that you see that the preview below spaces out the text into separated columns.
- Click Finish.
- Click Okay once you have chosen the top left entry coordinate for your data (such as $A$1).
If you are manually doing it, it is still possible, but only if you have one column of data per row of text. Then all you need to do is copy (Ctrl/Cmd+C) the entire singular column, and then paste (Ctrl/Cmd+V) in any cell in Excel.