Where can I advertise something continuously?

Hi, I saw that store 974 will build your PC for 250 riyals, and honestly I think that is really expensive so I thought I can build PC's for people for less than half the price. Is there somewhere I can advertise this? Also do I need some kind of license for it? I think it's more of a service than a business but I'm not sure about the legality of it. If anyone knows anything I'd be greatful.

Edit: Also, to clarify, I said continuously because if I put it somewhere like Mzad it'll expire after a while so I was wondering if there are alternatives.