Drop 4 integrators (1/s) into your model, do not connect them to anything yet.
Draw signal wires leading in and out of each integrator.
Enter names for each signal wire like so
Integrator Input Label Output Label
1st x1_dot x1
2nd x2_dot x2
3rd x3_dot x3
4th x4_dot x4
Use your four equations dx1/dt, ... dx4/dt
to quide what signals and operations should be wired together to form the signal x1_dot, ... x4_dot
