There are two ways to do this. If you don't like to work with command line tools, then you can upgrade Magento from System Upgrade in admin.
Login to Magento Admin and Go to
System > Tools > Web Setup Wizard
Here there is an option "System Upgrade"
Other way to upgrade is with command lines which I like the most as it's just matter of typing some commands and your Magento is upgraded.
Go to terminal and go to your Magento root directory and run following commands.
composer require magento/product-community-edition 2.0.2 --no-update
This will update your Magento. After update do some clean up and indexing with following set of commands.
rm -rf var/di var/generation
php bin/magento cache:clean
php bin/magento cache:flush
php bin/magento setup:upgrade
php bin/magento setup:di:compile
php bin/magento indexer:reindex
And you have updated Magento 2 version.