how can I start using the importer for Caffe models in Matlab?

I have my own convolutional neural network and I want to train the network using Caffe package in Matlab R2018a. I installed the importer for Caffe models in Matlab. I used the following link to guide me how to start using caffe model to train my network step by step https://www.mathworks.com/help/deeplearning/ref/importcaffelayers.html . however I have some questions:

1. the first step after installing the Caffe package is to download the required support package by typing importCaffeLayers at the command line. however, when I typed this command at the command line , I have the following error:

>> importCaffeLayers

Not enough input arguments.

Error in importCaffeLayers (line 71)

params = nnet.internal.cnn.caffe.CaffeModelReader.parseImportLayers(protofile, varargin{:});

Does anyone know what does this error mean? and how to fix it?

2. To import the layers of Caffe network I should use the following commands:

Specify the example file 'digitsnet.prototxt' to import.

protofile = 'digitsnet.prototxt';

layers = importCaffeLayers(protofile)

Can anyone help me on how to prepare the .prototxt file protofile that defines the network layers?

Any help will be appreciated