Hello all, I've recently been learning how to use th Airbus X and it's extremely realistic however I'm falling on some parts. If you guys could help me out I'd appreciate it!

How do I activate speed hold? (right click or left click? What's the little circle next to speed hold for?)

How do I activate heading hold? (right click or left click? Again, what's the little circle next to heading hold for?)

Where about is the NAV1 Audio Selector? I really need to turn it on!

How do I activate altitude hold? - (once again, right click or left click and what's the little circle next to altitude hold for?