I don't have any experience with applying or working for the VA but I do work for local government and I imagine their process is similar. Applying for a civil service position is about understanding their process and how to get onto the eligibility list. I wholeheartedly agree with other advice given, complete the employment application fully, don't rush, and double check your work. The first level of screening with local government is demonstrating you meet the minimum qualifications so your application is reviewed and decided by HR professionals, not the hiring department. If your application doesn't pass the initial review, it doesn't move forward.
If you pass the first review and there are lots of applications, your supplemental responses to the questions that may be included in the application will play a huge part as to whether you move forward. Answer each question thoroughly and in full sentences. They are reviewing your writing skills as well as your experience with those questions.
If you are invited to the first interview panel, please note they are often called an oral exam. It is an exam and you must pass. Having a 2-3 minute opening statement that summarizes your education, training and experience that makes you the best candidate for the position is important. Usually, they give you a chance to make a closing statement at the end of the oral exam, that closing statement is just as important, leaving the oral panel with a strong lasting impression is important.
Practice your interviewing skills with others or in front of a mirror to reduce your nerves in the oral exam, being nervous is normal but you want to be able to control it and practice, practice and more practice will help reduce your nerves and make you feel confident.
Lastly, don't give up. You may potentially get a lot of rejections or place low on the eligibility list or maybe not even place on the list at all since some only take the top 5. Since it is an exam, you can improve your skills and oral presentation and apply again.