So I suggest you train yourself first. You can ask the local construction committee when their construction post training will be held and how the training courses are.
2, first find relevant books to make up, such as the builder's manual of building engineering. You can have a look for yourself and get a general idea. So you can see something when you go to the scene to apply for a job. Above all, you must learn how to read architectural drawings. You don't need to be proficient at present, but at least you should know what the symbols mean. Do construction, don't know the construction drawing, no one dares to recruit you.
To sum up, you should buy some books on building construction, such as the builder's manual of building engineering, drawing reading of building engineering, 03G 10 1 atlas. In particular, the 03G 10 1 atlas is the key to identify the architectural structure diagram, and it is also a necessary atlas for reinforcement drawing.
When you have the relevant knowledge and certificates, you can go to the construction site to find a job. At first, the salary was low. After you gain experience, the boss or project manager will give you a raise.