Step 1:  

Start with the usual cleaning up commands at the beginning of a program:

clear;
clc;
close all;

Now create a network with two hidden layers. Each hiddeen layer should have 7 nodes.

mynetwork=feedforwardnet([7,7]);  

Note that you don't have to specify the number of input nodes or output nodes because these will be determined automatically by Matlab based on the structure of your data when you train the network.