Information on gaining a new Prime Minister can be found on Wikipedia at:

CLICK HERE where the Election procedure is described in detail,

There are 5 candidates.  An ballot system is used to select two candidates to go forward to the general membership of the Party.

Eimination ballots will begin within the Conservative Parliamentary Party on Tuesday 5th July. The candidate(s) with the lowest votes is eliminated in turn

The two candidates selected by the Parliamentary Party with most votes are then put to the full membership of the Conservative Party in a postal ballot. Each Party member, on a "one member one vote" basis, votes for their preferred candidate. The postal ballot goes to "all the members of the Conservative Party in good standing who have been members for not less than three months