Amplitude vs Frequency plot

I have a steady response formula ysteady(t)=18 + 6sin(240*pi*t - 0.120).

I need to write a script that plots the amplitude spectrum (Amplitude [V] vs Frequency [Hz]) using a sample of 64 values sampled at 512 samples/s. The spectrum has a resolution of 8 Hz.

I am very new to MATLAB, please help.

[darova]

Please show some of your attempts. Start from plot

[Igor Arkhandeev]

This example is so simple. Try to change it for your target.

t = linspace(0,2*pi,100);
ysteady(1:length(t)) = 18 + 6*sin(240*pi*t - 0.120);
plot(t, ysteady);