On our website in the support section of Twixtor there are tutorials and sample projects, that complement the documentation that is installed in the folder where you installed your software.
Are you using this in AE?
If so one way is to just drop the footage into a comp, set the comp duration to desired length (in comp settings), then make a new comp from that comp (select comp in project window and File|Mane New Comp…) and apply Twixtor to that (using the speed slider if you are not animating the slowmo)
Pierre