So just to clarify, you are the beneficiary of a will and the will maker has passed away, and you have not yet been vested with the property. Is this because you are a minor (under 18) or because there is some condition in the will that you need to satisfy beforehand?
The will should name an executor. This executor will need to first obtain grant of probate. If the will did not also name a trustee to look after this trust, the executor decides who to appoint as a trustee. In the meantime, the executor is the trustee. The executor may decide to act as trustee personally, in which case they will need to appoint themselves as trustee.
In practice, I would recommend you speak with the executor and nominate a trustee (over 18 and of mental capacity). However, it is your executor who has the ultimate right to appoint.