If you need plotting capabilities but the current computer where you are in does not have Jmol or Molekel installed, you can run JSmol, a javascript version of Jmol from our website. Just go to the Utilities tab in the top menu and select "General Jmol Viewer". It will load a sample molecule by default.
In the graphics area, you can click the right-hand side mouse button and goto File->Load->Open local file to open a file from your computer, it works with the files we usually handle in the lab (.xyz, .cube, .MOLDEN).