Clients who bought options can exercise American Style Stocks Options anytime except on the last trading day. One should bear in mind that if the margin utilization level is not sufficient, the exercise prior to expiry might be blocked.
For European Style Stock Options, clients can only exercise them at expiry.
You can see the exercise style of an option in Trading Conditions.
More information on margin utilization spike before option expiry, please check here.
If you want to exercise your option, you can click on the position and choose "Exercise".