The primary level of the SNP’ party’s organisation are the local Branches. All of the Branches within each Scottish Parliament constituency form a Constituency Association which is composed of delegates from all of the branches within the constituency.
The Constituency Association coordinates the work of the Branches within the constituency, coordinates the activities of the party in the constituency and acts as a point of liaison between an MSP or MP and the party. source: snp.org
The graphic below shows the constituency association role in greater detail.
The annual National Conference is the supreme governing body of the SNP and is responsible for determining party policy and electing the National Executive Committee.
The National Conference is composed of: delegates from every Branch and Constituency Association, the members of the National Executive Committee, every SNP MSP, MP and MEP, a number of SNP local councillors, delegates from one of the SNP’s Affiliated Organisations i.e. Young Scots for Independence, the Federation of Student Nationalists, SNP Trade Union Group. There are usually two National Conferences which usually take place in Spring and Autumn.
The National Council serves as the SNP’s governing body between National Conferences and its decisions are binding unless rescinded or modified by the National Conference. The party’s leadership is vested in its National Executive Committee, which is made up of the party’s elected office bearers and six elected members who are voted for at conference. The SNP MPs, MSPs and MEPs together with councillors and members of the Trade Union Group, Youth wing and Student wing have representation on the Council.