I just found this tutorial and found it great, really helped me.
I had initially the problem that when I did "intersection" nothing happened, just wanted to share my solution here:
I had to select the text I had in the circle (actually a rectangle in my case but that's of no importance)
letter by letter, with the
node tool

, doing "union" one by one. I mean:
- select the first letter with the node tool
- shift-select the second letter (adding it to the selection)
- do Path -> Union (this turns the first two letters into one "object" or path)
- shift-select the third letter (adding it as a selection to the still selected previous two)
- do Path-Union (this adds the third letter to the former two, turning them all three into one object)
- repeat shift-selecting the remaining letters and doing after each selected letter Path -> Union.
After this, everything worked fine. Many thanks to the original poster.