The rapid growth of the offer of available educational resources raises the issue of their appropriation by teachers. Although the term appropriation is widely used in mathematics education research, there is no clear conceptualization allowing researchers to understand the processes involved. In this paper, we attempt to fill this gap by proposing a model for studying appropriation of curricular resources by teachers. This model was elaborated drawing on conceptualizations of appropriation in social and management sciences and on the instrumental approach. It was then put to the test in an empirical study involving one kindergarten teacher who was offered a digital game for teaching and learning enumeration, in order to build and enact a teaching sequence using the game. The model is used as a framework for analysing the interactions between the teacher and the resource during the teaching sequence preparation and its enactment. Such analysis enables the highlighting of the teacher's transformations of the resource, aiming at adapting it to his needs and to the context of his classroom (instrumentalization), his choices of instrumental orchestration, as well as the evolution of his professional knowledge and practice (instrumentation).