If your really serious about doing this depending on the idea you have you need to do a few things. First of all find people that will have a positive impact in the business and can bring something to the table. Potentially interview people to help with this process. The way to stop someone stealing the idea is to use NDA’s or Non-Disclosure Agreements. In these agreements the person who signs agrees not to disclose the idea to anyone else and there are consequences if they break this as NDA’s are legally binding. However it can be expensive to get these properly written by a lawyer so weigh up the benefit. Let me know if you have anymore questions :)