Nothing is preventing you to apply your AC signal on top of the DC biasing voltage to have oscillations around that point just by cascading the two sources. Depending on the simulator, you might in fact find a parameter named DC inside the AC generator.
In a more realistic situation you can AC couple the signal to the bias: the AC is connected through a capacitor to the input and you can connect the DC to the same node through a resistor. Now you have a time constant RC which should be much greater than the period of the lowest frequency applied to the input to perform good decoupling