HR budgeting is a full process. Usually, there is a format to put in the proposed expenses during the year.
You need to check what all comes under the purview of HR. For example, recruitment, training, salaries, and statutory compliance. Sometimes, there are some administrative functions that are also part of HR. Also, take expense figures from finance for the previous year to understand the trend.
The expenses are then broken into monthly/quarterly figures. For example, if you propose to have four training programs during the year, which will cost 4 lakhs, then you plan when you would have these programs and put the expenses in that month/quarter.
Based on your proposal, Management decides how much money they can spare for which activity and which month. Finance tracks these expenses, and you get monthly budgeted/actual expenses.