If it's the rear brakes that have seized then yes, give the drums a clout with a large hammer on the front face by the wheel studs but not on the sides as that could distort the drums. Also, look behind the drums and give the arms to which the cable attaches a moderate clout towards the drums - this in itself may release the brakes a bit so the drum turns. The drum will need removing and everything cleaned up and unseized and possibly new shoes and wheel cylinders too.
The handbrake light staying on may be an issue with the switch beneath the lever itself or has the brake fluid level dropped in the reservoir.
If the fronts have seized it can be a bit more of a "game" to free them off. Sometimes they will turn with the car jacked up and a breaker bar on one of the wheel nuts but don't overdo this and snap a wheel stud. If they are really stuck you will have to get the pads out which will probably mean hammering them out and ruining them. Once you have a pad out see if you can lever the caliper piston in a bit then try pumping it out with two or three pumps on the brake pedal. If so all good but if the car has been standing a long time I would recommend you either rebuild the calipers yourself with new pistons and seals or better still get a pair of new or recon calipers if you are not that mechanically minded.
With the brake system, if the car has been laid up for a long time I would recommend fitting new seals in all the hydraulic system, new flexible hoses front and back, a thorough inspection of the condition of the brake pipes and finally bleeding through with new fluid.
Hope this helps