I'm representing myself in a DUI case I received a notice of endorsement for Witness from the da how do I request an endorsement

redirecting to the DUI section of this service

While you do have the right to represent yourself in a criminal case, it's almost always a terrible idea. The law allows for people to represent themselves as a pro se party. However, lawyers are trained to think, read, write, and argue in a very specific way. As a pro se party, the Judge will treat you as if you have the same knowledge, skill, and training as a lawyer. Proceeding without a lawyer is full of pitfalls and traps for the layperson, it’s usually a bad idea. Bluntly, if you mess up your case, you will be stuck with the consequences. To put yourself in the best situation and protect you rights and freedom, contact a DUI Attorney most will offer a free consultation and some will work with you on payments. Do your future self a favor and hire an Attorney who know what they're doing.

Hire an attorney or ask for a public defender.

If you are talking about witnesses you intend to call at trial, then you do not request an endorsement; you endorse them. You need to do the same thing the prosecution did: file a notice with the court, and send a copy to the other side, listing the witnesses you intend to call. Just to add my voice to the others, representing yourself in this case is a really bad idea. You should get a lawyer ASAP.