You got to feed it a bunch (tip use ure berry pot  if ure low on them) and when it fully healed you get some milk tank milk and a tm I believe and  you can also buy it then

If you got yellow forest walking path for poke walker and get very very very very lucky you can get it as dowsing item  I gotten 3 light balls from it shud work for both versions I actually beaten red while I had a pikachu whit volt tacke in my team  epic if you ask me