What is the parallel computing script to run this curve fitting code

I ran the code below with 6 stocks and it is fine. However when I tried to run with 21 stocks it get so long to calculate that I have to shut it down. Because of this I purchased the Parallel Computing Toolbox to make the code run. However I don't know what to include in this code to make it run with parallel computing. Please, could you let me know ?

lowerTail = 0.07; 
upperTail = 0.93; 

for idx = 21:-1:1 
currentRet = returns(:,idx); 
marginal{idx} = paretotails(currentRet, lowerTail, upperTail, 'kernel'); 
U(:,idx) = cdf(marginal{idx}, currentRet); 
end 

%%THIS PART BELOW IS THE ONE THAT I NEED TO USE PARALLEL COMPUTING TO RUN IT 

[rho, nu] = copulafit('t', U);