swipe finger from the left of the screen (outside of screen), towards right (into the screen). then a cursor field should appear. click on it and a red line will cross it which means that the cursor is locked.

with this cursor you can mark up any text and copy it with CTRL + C or click on the top bar of your browser and click the "Copy"-button.

then you can go anywhere and paste it with CTRL + V or click on top bar and choose "Paste".

take a look at the wiki next time:
http://wiki.maemo.org/N900_Shortcuts_and_Gestures