There are fairly straight forward options for this sort of thing... the simplest of which is you hash onto the field and check if the result is on the curve by

There are fairly straight forward options for this sort of thing... the simplest of which is you hash onto the field and check if the result is on the curve by applying the curve equation (which it will be with probability 1/2). If it is, you are done, if not increment the hash input and repeat until done. There are fancier ways to hash onto curves that can give nearly uniform points in constant time, but they're curve specific... and for parameter generation you don't need constant time.