Hi,
There are two way that you can do that -
1. Upgrade the current version of SEPM to latest one and then autoupgrade the SEP clients.
https://support.symantec.com/en_US/article.HOWTO80780.html
2. You can import the SEP packages of new version to your current SEPM and then use auto upgrade to install them on systems -
You need to download the full install package from fileconnect and then extract and go to -
\Symantec_Endpoint_Protection_14_MP1_Full_Installation_EN\SEPM\Packages
you can then use import wizard on sepm to import .info files.
then use auto upgrade.