Questions about Celestron NexStar 4SE Computerised Maksutov

I got the telescope for some time now, I have tried everything, read all the instruction in the manual but I am still unable to focus it. I can't see anything clear, I can just see light but nothing else. I made sure I have flied the mirror, etc. etc but still can use it. I am trying for example to simply see the moon. I can just see bright light but nothing else...I have a 15 mm and a 25 mm eyepiece...tried both but nothing works. Same result.

What additional parts do I need for my Canon 6D Mark ii with a Sigma 35mm, f/1.4 DG HSM ART lens for night photography?