You are able to make investments at any time in your EasyEquities account by making use of a buy instruction.
A buy instruction is created when a trade is placed outside of market hours or during an intra-day auction. Your buy instruction will be converted into a buy trade when the market opens on the next trading day or once the intra-day auction has ended.
To read more about buy instructions and how they work, read this article.
Take a look at the different trading hours for the account types here.