Activity in Android studio represent a Window, where you can dispplay controls and handle data etc. You can start as many form/activity the project requires. Just add a new Activity and do the following

Here we goes

• Create a Intenet object, the first parameter will be the package or Main activity and the second will be the new new activity class
• Call the startActivity method

Code

Intent intent = new Intent(MainActivity.this, NewActivity.class);
startActivity(intent);

Note: Can also possible to run as many activity with in a activity using the concept Fragment (Learn More about Fragments )
I hope this will help you