A simple thing like copy and paste might have you flummoxed in a browser-based program. You can copy and paste text, but only if you use keyboard shortcuts. And text you copied outside of Excel Online will probably be pasted as plain text, which means that formatting (things like bold, italics, and hyperlinks) needs to be re-applied.
For best results, use keyboard shortcuts, not the right-click menu or Clipboard commands in Excel Online.
Press CTRL+C to copy, CTRL+X to cut, or CTRL+V to paste the text (Windows); or press ⌘+C, ⌘+X, or ⌘+V (Mac).
Tip: If paste isn’t working, you’re probably looking at Reading view. Switch to Editing view: Go to Edit Workbook > Edit in Excel Online.
To reapply text formatting like bold or italics, select the text you pasted, click Home, and then click the formatting you want.
If you’re pasting a hyperlink, you’ll have to reconstruct it:
Right-click the cell, and then click Hyperlink.
In the Text to display box, type text you want to show in the cell.
In the Address box, type the web address of the link (URL).