Step by step- applying a gradient from a downloaded file to text

hey.

i want to apply a gradient that was applied to a square in a file I've downloaded into text from another file. despite my best attempts, i do not understand swatches (other than that they are presets) and i do not understand how the program works in relation to gradients.

i'm sure this has some answers online, and I've tried to look for them, but illustrators super unintuitive nature, making every step that should be simple a chore from hell, along with the horrible tutorials that explain a million things you never need to know while making sure you have as hard a time as possible to find out what where you do need to know is have really pushed me to the end of my patience. i had to go to sleep just to make the urge to punch my monitor go away.

thanks in advance.