// 打开文件
using ExcelPackage package = new(new FileInfo("path/to/file"));
// 打开工作表
ExcelWorksheet worksheet = package.Workbook.Worksheets["sheet_name"];

worksheet.Cells.Clear();

// 读取指定坐标内容
var value = worksheet.Cells[row, column].Value?.ToString();
var value = worksheet.Cells[row, column].Value?.ToString().ToInt();

// 写入指定坐标内容
worksheet.Cells[row, column].Value = "NewValue";

for (int row = 1; row <= worksheet.Dimension.Rows; row++) {
	for (int columns = 1; columns <= worksheet.Dimension.Columns; columns++) {
		worksheet.Cells[row, column].Value
	}
}

package.Save();