Press D on your keyboard to quickly reset Photoshop’s foreground and background colors, which sets black as your foreground color. Then use the keyboard shortcut Alt+Backspace (Win) / Option+Delete (Mac) to fill the Background layer with black:
Press X on your keyboard to swap your foreground and background colors so white becomes your foreground color. Select your Type tool from the Tools palette or by pressing T on your keyboard. Choose a font from the Options Bar at the top of the screen, then click inside the Document Window and enter your text. I’m using "Times New Roman Bold" here to keep things simple if you want to follow along. I’ll enter the word “GOLD”: