As @J.R. points out in the comments, "officially" can be added in more than one place in your example sentence.
Officially, the graduation year is when the dissertation will be added to your curriculum.
The graduation year is when, officially, the dissertation will be added to your curriculum.
The graduation year is when the dissertation will officially be added to your curriculum.
The graduation year is when the dissertation will be officially added to your curriculum.
The graduation year is when the dissertation will be added officially to your curriculum.
The graduation year is when the dissertation will be added to your curriculum officially.
NB: "master's" has been removed for formatting considerations
All sentences have the same meaning, it is a matter of style.
Saying "officially added to your curriculum" may be redundant since once something is added to a curriculum it is usually "official".
The sense of you sentence can also be expressed as
A dissertation is added in your final year for fulfilment of the requirements.