I went to hospital .im 10 weeks pregnant now and the us shows that i have low lying placenta partially covers the os grade 0 . what to do?

Nothing to do: This is called placenta previa. It is usually graded from 1-4 wth one being the mildest so a grade 0 would be very mild. There is nothing to do about this and will not cause you any problems until later in pregnancy. Even then it may not cause a problem because yours is so mild. As you get later in pregnancy you will just need to be checked if you have bleeding.