Practicing from past CFA exam or mocks should be a key part of your last 2 months of exam preparation.
However, you should know if these past exams are relevant to your exam.
Update: IFT provides a relevancy for only past Level III 'essay' exam past papers. For details please see below.
Level I and Level II: CFA Institute publishes many relevant practice questions and full mock exam on their 'student portal' which is available to exam registered candidates (login is required). The source of these questions includes the past mock exams. Hence if you want to practice with past CFA Institute published materials -- then the student portal is your best source for questions relevant to your upcoming exam.
The 2018 June exam relevancy document is available at this link: Essay Exam Relevancy Document
IFT does not publish a relevancy for the MCQ Exam for Level III. Please note that CFA Institute publishes MCQ practice questions on the student login portal which are of course relevant and you should do for practice.
(Please make sure you also login to CFA institute portal to practice the problems that are provided there)