How to evaluate an impulse/response model in MATLAB
One way of evaluating the model response to arbitrary data is the lsim command. As you don't provide more information with respect to your data and/or model an example below (taken straight from the MATLAB help). See help lsim or doc lsim for more information. 

% create model
%
num = [1 4];
den = [1 20 5];
G = idtf(num,den);

% evaluate response
% 
t = 0:0.01:5;   
u = sin(t);   
y = lsim(G,u,t);

% plot
%
figure;
plot(t,y)  


In addition, if desired, you can evaluate the model impulse, step and/or frequency response using the impulse, step and bode commands.