A boostrap for the wallet can be downloaded from:
http://ds1.nav.community/bootstrap.tar.gz
NOTE: this may take some time as the blockchain is around 4.7GB in size
You simply need to replace the chainstate and blocks folders inside your NavCoin data directory with the ones from your bootstrap.
To find the data directory please see this article
Bootstrapping is the process of adding a pre-synced blockchain from a trusted source to your wallet, allowing you to skip part or all of the blockchain syncing process.