Show all updates available for solution
get-package -Updates
See all available assembly versions
get-package EPiServer.CMS.Core -ListAvailable -AllVersions
Install specific package version
install-package PackageName -Version X (where X is the version you wish to update to)
e.g. install-package Episerver.CMS.Core -Version 7.6.0
Install latest version for specific package
install-package PackageName
e.g. install-package EPiServer.CMS.Core