First, you just have to download the Selenium Plugin:
Jenkins > Manage Jenkins > Manage Plugins > Search for Selenium Plugin and Install it
After that you should see a Selenium Grid tab on your Jenkins dashboard. Click on in and you should see a Hub already running, you can also restart the hub in this page.
Then you have to configure your nodes, for that:
Selenium Grid > Configurations > New Configuration.
Here you will probably want the match all nodes option and Custom web driver node configuration. Now you have only to specify where your drivers and finish the configuration.
Selenium Grid > Configurations > Nodes matching configuration > Click on the configuration you just created > Click on Start.
Now if you click on the Selenium Tab you should see not only your hub online but also, at the bottom of the page, there should appear your node as a registered remote control.