Adding surname/last name

My Name is Digvijay and currently working in  IT company. I have only first name(i.e. Digvijay) in all my documents. Now a days last name field is mandatory at some places. So I want to add surname/last name. My Father's name is Chandeshwar Singh, so I have decided to add "Singh" as my last name.

So, how can I do this? and if my name is changed, will it create problem for me, because, now  it is not possible to change name on all academic records. 

Please suggest me.