You can re-apply at any time and your new application will be considered on its merits. You should be aware, however, that if there has been no significant change in your circumstances since the last refusal, or if you are unable to address the reasons for refusal, your application may be refused again. A previous refusal will not though, in itself, mean that any subsequent application will be refused automatically.
Please be advised that should you re-apply then you will have to complete the full application process again. You should follow the same set of steps outlined on our webpage 'How do I apply for a visa'.