Your business is a disregarded entity and you file it on schedule C in your personal tax return. The "loan" doesn't go on your tax return. It is just a transfer from a personal account to your business account. It's just moving funds from one pant's pocket to the other pocket. It's all personally yours. You just enter the actual expenses you spent it on. So sounds like you will have a Loss on Schedule C which can be deducted on your tax return.
Oh, what kind of business entity is it? If you are a Single Member LLC that is an S corp it is reported a different way. And schedule C is for self employed, sole proprietor, freelance, etc. and not for a joint business. You said "our small business". You might have to file a separate partnership return. What state are you in? I don't know how Married Joint venture works. I'll have to look around for some links.
And...if you take money out of a retirement account you will get a 1099R in January or February that must be entered on your tax return.
To enter your retirement income, Go to Federal> Wages and Income>Retirement Plans and Social Security>IRA 401 k) Pension Plan Withdrawals to enter your 1099R.
Please be careful about "our small business." A small business owned by two or more people (even spouses) is handled differently from a small business owned by one person.
If the business is not an LLC, and both spouses materially participate in business activities, then you can either
a. make one spouse the owner, file one schedule C, and make the other spouse an employee or subcontractor
b. or file two schedule Cs, each listing each spouse's share of the income and expenses.
If the business is an LLC, and the two spouses own the LLC, then
a. if you live in a community property state, you file two schedule Cs, each listing exactly half the income and expenses,
b. if you don't live in a community property state, you file a separate form 1065 partnership return. The partnership return generates a K-1 statement for each partner that goes on their personal form 1040.