WiFi icon does not appear on the taskbar. [SOLVED]

You need to add systray to the shelf contents (perhaps called panel contents in your language). Since your screenshot shows the module is loaded, it should be available to add. Right click on your shelf/panel and select contents on the shelf menu.

Looks like systray is loaded, (Bandeljo do sistema) which means you should see wifi on the shelf. Seems to me it might be an issue with your wifi card rather than the systray module. Systray contents are added automatically. Do you know what wifi card you have? If not
inxi -N in the terminal will tell us.

Edit - Having said that, are you connected via wifi?