as your matrix is 4D....you can read the variable 'var' of your interest in the following way... data = ncread(ncfile,'var',start,count,jump)..
where start,count,jump will be vectors of size 4X1 (because you are dealing with 4D data)...default values of jump is [1,1,1,1]...you can put your interested number, jump will skip the data by the numbers given in the vector jump.
If count is [inf,inf,inf,inf], it will consider the matrix till the end. This will specify the end point of the data.
If start is [1,1,1,1], matrix will be read from first position of each dimension.
Reading your own interest data is pretty straight forward by varying start,count,jump. Read the documentation multiple times, it makes things clear.