To be making a will is to be making a promise to ourselves over future action. It may also have overtones of attempting to look after those we love and care about.
To inherit from a will means that we need to look at the habits, characteristics and morals we have inherited from our ancestors.
We mav dream of a will at a time when we need everything to be done properly and with certain levels of correctness. There is the obvious play on words where a will would indicate the will to do or to be - the determination to take action, for instance. Because for many making a will is a very final action, in dreams it can indicate a recognition that we are entering a new phase of life.
Determination in spiritual matters is represented here. This can also suggest the resolution of a problem with which the dreamer has been dealing.