IPRally is a fast and intuitive tool for making novelty searches and invalidation searches, for example. The basic ways of getting started with a search case are explained here:
A. If there is no written material of the invention at hand, building a new search graph may be the way to go. Just type in the key features and arrange them in a technically meaningful order in the graph. For example, the graph below is created by typing "vehicle [enter] engine [enter] cylinder [enter] is arranged non-vertically". Sibling features are added by pressing shift+enter. More keyboard commands are shown here.
B. If you want to invalidate, i.e. search prior art for, an existing patent or patent application, just type in the publication number to the publication number field. Then select "Claims and description" for a smart search or one of the independent claims of the publication to find prior art for a particular claim.
C. To use free text for making the search, you should use the third option available, i.e. the free text field. Claim-type or at least patent-type text is the optimal input, but you can expect good results also with any technical descriptions, like parts of scientific articles or invention notifications. The character limit in the field is 5000 currently.
Finally, press Search patents to see the results.