Thanks for your question.
Either could petition the other on the basis of their adultery. The person with whom one has been adulterous with need not be named in the divorce petition.
If you wait for a further 6 months then you could petition on the basis of a two year separation with the consent of the other party to the petition.
Alternatively either could petition the other on the basis of their unreasonable behaviour. The should mostly be related to most recent behaviour and it can be things like not speaking to you, providing you with emotional support, verbal (eg. Nagging, insults etc) or physical abuse, unwillingness to engage in typical things that married people do (socialising, eating together, planning practical matters together), not contributing towards the expenses of accommodating yourself and the children (if any), not engaging in physical affection, not helping you with children.
You will need to submit a petition to Court whichever way above that you opt for. You will need to submit your marriage certificate.
There is lots of useful advice for lay persons considering divorce here, including how to complete and submit a petition:-
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