Sciatica can present differently for people depending on what is causing it - disc, piriformis, spinal stenosis and where and how much the nerve is compressed etc.
For a lot of people sitting and lying is painful and walking/standing gives relief. For others it is the opposite. Different exercises, movements will work for the different causes.
Where and when are you feeling pain? Is it in your back, calf, foot? Is it worse in the morning, all day, evening? Are you pain free lying down, sitting, standing, walking? Does bending forward or bending backwards cause more pain?
During the acute phase avoid any exercises which involve bending, lifting or twisting. Avoid sitting as much as you can ( especially with bad posture) , if sitting get up and walk around frequently. Walking is great, if it is pain free. If you can walk for 5 minutes pain free, do that. Try the same tomorrow. If that is pain free try 6 minutes the next day. With sciatica do not walk through the pain. The nerve is very sensitive and is very easily irritated.
This is an analogy my consultant gave me. Imagine you have a cut and you keep picking at it, it won't get better. You need to give it a chance to heal.
For the vast vast majority this will get better with time.