assuming you started with a sole proprietorship (no S-corp election) you have now formed a partnership and there is now a need to file form 1065 - partnership return. if the money from the other partner was left in the business you do not have a taxable event. if you took some or all of the money out it's capital gain to the extent it exceeds your basis. I strongly recommend that you use a tax pro to make sure there is proper reporting.
the profit before the partnership was created would still need to be reported on your Schedule C. the partnership income and expenses are for the period starting on the date the partnership was formed.
