Dear,
first of all congrats for your job.
This is your first job, so i will suggest you to not to focus on a particular fields, this is your learning time. do all the job given to you. it will help you to understand HR profile in a depth manner.
There are many fields in HR, as time passes by ypu will automatically understand in which domain you are best.
Doamin of HR-
Recruitment & selection, Generalist, Pay-Roll, Statutory Compliance's, Industrial Relation, Personal Management, Planning and Development, Organisational Development, Human Resource Development (through Learning & Development, or through Training).
Best of Luck for your future..