One year after graduation, you can get an assistant engineer (this company can handle it for you directly). With the help of the assistant engineer, you can sign the design on the drawing. (Inspection and review cannot be signed at present) The design can only be inspected after 3 years; Assistant engineer for 4 years, you can take the exam as an engineer, which may be a bit difficult. According to the national standards, if everything goes well, you can only get the audit certificate seven years after graduation (one year as an assistant, three years as a designer and three years as a verification).
It depends on what certificate you took. D-level can only be designed as D-level, and A-level can also be obtained. With A-level certificate, you can design A-level. This is just your own. If the company doesn't have A-level qualification, you still can't design (or, if you design, the company can't stamp you, or it's just a piece of waste paper).