Add er to many short adjectives for comparison and use more with many longer adjectives. Put than before the second option.
Practical examples
This room is quieter than that one.
هذه الغرفة أهدأ من تلك.
The train is more comfortable than the bus.
القطار أكثر راحة من الحافلة.
Today is better than yesterday.
اليوم أفضل من أمس.