Welcome to Fluther.
First-time questions can be a little off-putting, not knowing exactly what to ask, or what the responses might be like. So you’ll get a pass on this one, of course. Because you already know the answer: the only way to improve your English conversational skills is to have conversations in English. Obviously.
Preferably, you should have those conversations with native (or fluent) English speakers who will also be willing to give you knowledgeable feedback on your style – when you’re ready for that. But before then you should start by having conversations in your head and with others who are at your level. The reason for that is so that you can realize in advance where your errors will be and move to correct them so that your first-person English can be acceptable to you first of all.