how to make a time shift function

We were asked to create our own functions (m-file) like a general time shift function.

I'd imagine it like this but i ran into a problem on how would I shift the time.

function y = myTimeShift (X, shift, t)
% time shift function.  X is a function of t given time (start:step:end).
?????????????????  What is in here so that x(t) is now x(tshifted)?

in the command,

t = -5:0.1:5;
x = myStepfunc(1, t);
y = myTimeshift(x, -2, t);
plot (??,y);

The myStep function is from heaviside(t). only with changeable Amplitude A. see below.

function y = myStepfunc(A, t);
%Step function with Amplitde A, maximum time, and minimum time.
y=zeros(size(t));
y(t>0)= A;
y(t==0)=0.5;
end