What is the process of filing a fiancee visa application for a spouse?

Here is a link to a resource made available by the USCIS regarding fiance visas: https://www.uscis.gov/family/k-1-process-step-step. Be aware, however, that the application process can be significantly more complex than might appear from reading that website and even from reading the immigration forms and the immigration statute. Errors in the application process can create large delays or even have more harsh consequences. It would be wise for you and your fiance to consult with an immigration attorney who, after learning all of the relevant information, could advise about eligibilities, options and strategies to attain your goals, and who then could offer legal representation in the often complex application process.

For starters, the processes are different for fiancees vs spouses. Are you married at this time? Also, where is your fiancee / spouse? In the USA? Or abroad? If your mate is in the USA, how did s/he enter the country? With inspection or without? Any criminal history?