I have been using the same version of electrum(v2.6) for quite a time now. I could not find any option to update it within the application.
I found that v2.7.11 is the latest version and there is security risk in the old versions (
https://bitcointalk.org/index.php?topic=1663652.0).
So, how to update Electrum on windows ?
If you used the installer, just install the new version over the old version. If you are using the stand alone version, use the new version and copy the wallet file if needed.