Open your PowerPoint presentation
Go to the Insert tab
Click Header & Footer
Select the Footer checkbox
Type the footer text you want
Click Apply to All to add it to every slide
Click Apply to add it to the current slide only
To edit an existing footer, reopen Header & Footer and change the text
Click Apply to All or Apply to save the changes
To remove the footer, clear the Footer checkbox and click Apply to All
If the footer does not appear, check the slide master or layout settings