Please follow the steps below to add a text box:
Step 1: Click anywhere in the worksheet;
Step 2: Click the "Insert" tab in the ribbon;
Step 3: Click "Text" and select "Text Box" from the list ;
Step 4: Hold your mouse and drag to draw a text box in the worksheet.
Please note, this will give you the horizontal box. Please "Vertical Text Box" by clicking the small triangle after "Text Box" to draw a vertical text box.