you just measure your state with all the states of your basis
Suppose your base is {|0>, |1>} and your state is |x> => you just need to compute P(x = 0) = |<0|x>|^2 and P(x = 1) = |<1|x>|^2
Suppose your base is {|0>, |1>} and your state is |x> => you just need to compute P(x = 0) = |<0|x>|^2 and P(x = 1) = |<1|x>|^2