......
Of course 'from' and 'to' doesn't exist. This is pseudocode. The "from" and "to" need to be replaced with your own values -- that of quaternions in this case.
If you are this weak in programming, don't even try to do this via code.
error CS0103: The name `from' does not exist in the current context...it tells you that 'from' doesn't exist. Look at the code. What's 'from'? It's not defined anywhere. So define it, set it to something.
error CS1501: No overload for method `Begin' takes `4' argumentsIt tells you that the Begin method doesn't take 4 arguments. Right click on the Begin method. Go to its definition. Bam! You can now see the function you are trying to call, including the parameters it expects. You should be able to figure out the rest.