If England are still in the tournament, which they will hope to be, they will have to vote either via post or via proxy. The players will have to register for a postal vote - ensuring they are on the electoral register - before June 19 but as they will not be in the country when postal votes are dispatched, they may be minded to appoint a proxy - normally a family member or a friend the player can trust - to vote on their behalf. The deadline for appointing a proxy is June 26.
The links for postal and proxy votes can be done through the GOV.UK website.