Dear Enrique, 

The Church does require that a prudent period of time elapse after you enter the Church before accepting you as a candidate for the priesthood. Usually this means at least a year and a half. The various orders and seminaries may have different policies in this regard, and you would have to contact each one for their own procedures.  

One of the reasons for the suggested waiting period is to make sure the conversion is sincere and stable, and the 'vocation' is a true call and not just the flush of conversion. It takes time to see that. Also, you can be sure that when you apply to a seminary they will look at more than just the time you have been in the Church.