first stop trying to start it remove the timing covers check if the belt is broke if not broke rotate it to top dead cent on #1 cylinder remove the crank pulley and what ever else is in the way the mark on the crank should line with the mark on the block the cam mark should line with the top mark either on the cover or on the head see if they are off first if they are replace the belt and re tension the belt to the spec in your book if you never done this you should have a book when it is tensioned correctly reinstall crank pulley and covers start engine .if runs ok no bent valves if not you will have to remove the head and replace any bent valves this is not a something for the in experienced person to do there is Alot more to it but that is the basic stuff you need to do if there are other things in the way you will need to remove them such as alternator belts or water pump etc get a book read it and then decide if you are up to the task at hand .