The first thing you could do is change the image

(I think they recommend 960 pixel wide x 275 high, but you can experiment)

then you can go to Plugins on dashboard left and configure Akismet, which will require a free Akismet account

then you could configure Jetpack which will require you to create a WordPress account

then could play around with all the Appearance and Settings menus

To do these things and explore WordPress in general, click on top left menu

have fun