Let your Chihuahua smell and investigate the place to introduce them. Soon, they will become familiar with and comprehend when it's time to use the loo.
Maintaining a regular schedule will do more for your Chihuahua than anything else.
If your Chihuahua has an urge, you may observe body language such as sniffing or getting agitated.
You can use any singular term you like, such as "potty," "outside," or any other. Your Chihuahua will quickly be able to link the word to the activity.
More of the exact same activities are repeated the longer you persist with something. Your Chihuahua will all learn eventually.