You must have a written purchase agreement - so the 'buyer' records what it says. The buyer might be you personally or a business you already own. Or 'you' might be providing money to the buyer to close the purchase.
If you bought business assets there should be an itemized list with values , or create one now. Then record the purchase of various fixed assets, intangibles, and even goodwill just like you bought from a regular vendor.
If you bought shares of a corporation then the entry will depend on if that entity is continuing to exist - or if its merging into another existing company or business.