Obtain the input impulse response h(t) and the system function H(s) of your system
A very simple system:
$ y(t)=x(t)\, $ and $ x(t)=\delta(t) $
We can get $ h(t)=\delta(t)\, $
$ y(t) = h(t) * x(t) dt\, $
$ y(t) = \int^{\infty}_{-\infty} h(\tau) x(t-\tau) d\tau\, $
