Welcome to the forums @JeZxLee!
For a Label node, you can set the Align and Valign properties to Center, which will center the text both horizontally and vertically.
For a RichTextLabel, which appears to be what you are using in the screenshot, there is no way to align the text vertically, but you can align the text horizontally by adding the [center]your text here[/center] to the bb-code, after enabling bb-code in the RichTextLabel settings. You can find the supported bb-code tags here.
So, if you need it to be centered both horizontally and vertically, you'll probably need to use a Label node rather than a RichTextLabel, or you'll need to manually position the text vertically via line breaks so it appears centered.
