So if we know the name of the function we want to call, we start typing that:
Once we open the brackets the box should pop up telling us what arguments we need to provide, ie the inputs for the function, with the one we are currently typing in highlighted in Bold. It shows the type of data required for each, and the name.

For the function to work we need to provide exactly those types of data in that order.
(actually some functions have overrides, so they can accept a few different sets of input types, but we can come back to that)
The names you give these inputs don’t affect the behaviour, as long as they are of the correct type.
We need to also create and name inputs for these on the Grasshopper component by right clicking the input names (adding more inputs if needed with the little + icon that appears when you zoom in)
We can also set the Type hint here, making sure we have all the inputs needed for the function.
When we open the script editor after doing all this, we should be able to see all these names and types we’ve just created at the top like this:
…and we can then plug them into our function
We can see from the description of the function here that it returns an array of Breps, so we can assign this to our output A by typing
A = Brep.CreateOffsetBrep(brep, distance, solid, extend, tolerance, out outBlends, out outWalls);
That’s pretty much it.
The one extra little complication here is these last 2 arguments which have the keyword ‘out’ before them. We need to create these variables first so the function can assign to them. We know they are both of type double array, so we can do this by adding this line at the start:
Brep[] outBlends,outWalls;
This is just a very short and incomplete guide, but hopefully of some use to get started with.