How to add to an ArrayList from another class in java? [duplicate]

This question already has an answer here:

• Adding objects to ArrayList from another class 3 answers
• Adding object of one class to the arraylist in another class 2 answers

I am trying to add objects to an ArrayList from another class in java. I have an ArrayList set up to hold names in a class and I want to add to that ArrayList from a main class. I also want to assign a random number for each object in that ArrayList. For example, I want to assign an account number to each user inputted object in the array list. I am very new to java and have no idea how to start this. Thanks