There are several ways to get help ingame. These are summarized below.
The campaign acts as a tutorial. Play through it to get used to the tools and features if you're new. Especially in the first few missions, the fundamental controls and construction tools are introduced step by step.
The context help gives you a little assistance while using a tool, statistic window or data layer. Simply press F1 (by default) or click on the button on the left side of the toolbar to open it. The content depends on the currently open menus or windows.
The guide system highlights features with a yellow color and assists with small hints when the player uses some features for the first time or is stuck a bit. It can be deactivated from the settings menu.