Practice! It's really the only way, but there are many types of speaking practice. If your level is very low you might want to just repeat English phrases you hear on TV shows or podcasts. From there, speaking to yourself to get more comfortable with English sounds and fluency is surprisingly useful. Talking to a friend or language partner is obviously a lot more engaging, and there shouldn't be any pressure to perform. Lessons with tutors will also help a lot, a good tutor will encourage you and help you improve without criticising you harshly. At more advanced levels, you might want to try learning an interesting/emotional/passionate speech from a play or movie to really stretch your expressive confidence. Having a language goal to work towards helps a lot too, a specific motivation for improving your English and become more confident makes it much easier to expand your comfort zone.

Keep speaking as much as possible! Don't be afraid to make mistakes. I can help you if you send me a message.