First position the cursor at the end of the second page, that is, after the last word on the second page;

Then, insert → Delimiter to pop up the Delimiter dialog box, and select Next;

Then, check the → Header and Footer, and click the previous link in the "Header and Footer" toolbox that pops up;

Click Set Page Number Format to open the Page Number Format dialog box. Click the starting page number and set it to 1 (or set it to any other page number you need) to confirm;

Click "Insert Page Number" in the "Header and Footer" toolbox to close the "Header and Footer" toolbox, and it's OK.