The configuration of your I2P is not a trivial job and takes some time and knowledge to do it the perfect way.
For luck I2P runs fairly well in default setup - as long as your PC have sufficient ressources to run I2P. Nevertheless you should at least setup the core settings bandwidth and connectivity on this page.

For more advanced setup and tweaks of your I2P router you need to select the links on the upper menu on site and adapt those settings to your needs and wishes.

configuration submenu

First point "Network" is already open and contains the bandwidth and connectivity settings you should already have aopted to your needs.
Second point Service contains options to start and stop I2P and the setting to open a browser on startup.
Next point Update tweaks the automatic update of your I2P router.
Tunnels page let you tweak current destinations for active I2P session only.
On clients page you are able to enable SAM bridge or disable unwanted webapps.
Peers page is ment to manual adjust single values for single routers, including shitlisting.
Keyring page prepares the functionality to encrypt your destination IDs and let user add a public key to local keyring.
On logging page the behaviour of the logs page is controlled.
Same on stats page for stats logging and graphs.
Last entry advanced finally shows you the box for all config line options.