You need a Photo Editor programme, if you search for - Photo Editor Freeware - there should be quite a few.
Your picture looks OK. Editing it to size should not be too difficult. The Editors are usually easy to use.
The cards are usually available in mixed packs at Stationary suppliers.

The book has been out quite a while and the patterns are mixed Salmon, Sea Trout and Trout.
It is no smooth, flashy production like many modern books, but is a mine of information on many older patterns.
It is well worth the fairly cheap price. (That from a Scot )