I am having difficulty calculating closing entries.
Could you explain in easy to understand terms how to calculate both dr. and cr. For income summary and then totals.

Step 1: debit all your revenue accounts and credit income summary.
Step 2: credit income summary for the cost of all your expenses, and then credit your expense accounts.
Step 3: credit income summary the difference of the income summary from your revenues - income summary from your expenses.
Step 4: Debit capital and credit withdrawals (both will be from the balance in your withdrawal account)

Example:
1.
Dr. Service Revenue 84,000
Dr. Interest Revenue 15,000
Cr. Income Summary 99,000

2.
Dr. Income Summary 66,000
Cr. Salary Expense 29,000
Cr. Supplies Expense 6,000
Cr. Depreciation Expense 12,000
Cr. Rent Expense 15,000
Cr. Interest Expense 4,000

3.
Dr. Income Summary 33,000 (99,000 - 66,000)
Cr. Capital 33,000

4.
Dr. Capital 20,000
Cr. Withdrawals 20,000