In the campaign form, paste one recipient per line as email,name. A header line is skipped. You can also save a mailing list and reuse it, or use the contacts in the CRM (in the Pro and Business plans), which accepts CSV files.
A classic mail merge, where each email takes any column from the sheet, such as an amount, is not available. The text can contain fields only for the recipient’s name and company: the name from the pasted line or the CRM contact, the company from the contact’s account in the CRM. If you need other personal details in each email, send those emails one by one.