Due to weather sudden weather changes you have to change the runway for landing. What are the steps to follow?

DEP/ARR page -> DEST Arrivals -> Select new arrival/approach -> EXECUTE -> Use LEGS page to close discontinuities ->PLAN mode to confirm it's what you want.

yep, thats it, select your runway and approach the same way you did while on the ground. Just be aware that this may change your TOD depending on approach, runway orientation. Just keep that in mind if changing while close or already in VNAV descent.

There's no magic way to switch it. After you switch the runway, look at the legs and make absolutely sure it's right. What I've noticed is that it will just add the new runway after the first one so you have to delete all the waypoints from the first one.