As you may have noticed, the sun is right above you and it's basically the middle of the day. To make the game simulate a different time of day, making the shadows longer etc., we go into the Environment Editor, which you can find under Tools. This is what it looks like:
It's probably a good idea to make the window bigger or maximize it on a second screen (if you have one) so you can see all the information properly, because it's all a bit squeezed together now.
This is the tool that is used to adjust a wide variety of environment factors. For now, we'll only change the time of day. This we do on the right, in the section with the long white line that runs vertically across the screen. In the bottom of this section, you'll see "Current: 12:00" (If you don't, expand the window until you do). This is the current time in the level, which means that the sun will be at its highest point and the shadows will be very small and only directly under objects.
To make it look like a different time of day, we'll simply enter a different time in the box behind Current or drag the arrow above the white line to the left or right. As you change the time or move the arrow, you'll see the time change right away in the Viewport, so you can see immediately what the level would look like at any certain time. For now, let's set it to 09:00. Our fishing trip has just started, after all. We have a whole day of fishing ahead of us.