How to obtain a QQ plots

Good morning! I'm trying to obtain a Q-Q plot of a column of 20 data with the matlab function qqplot(X,PD).

With the function quantile(X) I calculated the quantiles of my data ([.025 .25 .50 .75 .95 .99]) and the PD created is The 'gev'.

My goal is to obtain the representation of the bisector and further the confidence level of the 95%, but I don't know how to get all this.

Can you help me?

Thanks!

Marghe