17.1 will be available through the updates soon for current users of 17.0. As of this moment it must be downloaded then you burn the iso file and install it. Unless I missed something.
Probably referring to this
mint 17.1 info
One of the major advantages of this switch to LTS-basing is supposed to be that upgrades to point-releases can be done much more easily without requiring a complete reinstallation. This release will be the first test of that, and the release announcement says that upgrading "will be easy", and details will be announced in the near future, so just sit tight.