The first thing I'd do with a time machine is, of course, obvious.
The second thing is this:
I'd skip forward in time and collect the next few months' worth of National Lottery* draw numbers, skip back to 'my' time and set about winning vast quantities of cash every week until people started to get suspicious. I would expect the media to start flinging accusations and making flagrant remarks and allegations about my private life after the third week**, and the authorities to get properly interested after around a month's worth of jackpot wins. Once the media had started to kick up a storm and the authorities come knocking, I'd simply disappear for a few months***.
I'd then play on the media's continuing interest and announce that I would prepare and announce a press conference in order to release my secret. I'd then disappear once more for a month or two, popping up only to announce a live, in-person press conference for a given date and time. Every English- speaking country in the world would be led to believe that the press conference was to be hosted by their capital city, and the date and time in question would be some weeks in the future to allow time for debate, argument, speculation and fisticuffs.
On the date and time in question I would arrive at every venue in question simultaneously and give the same pre-prepared speech outlining my 'system' for winning the lottery. The 'system' would, of course, be a complete lie, utterly useless to everybody, and immediately obvious as both. I would finish the conference, leave and move on to item number 3 on my List of Things to Do When I Get My Hands On A Time Machine.
* I refuse to call it 'Lotto'. Stupid name.
** This, of course, doesn't include the Daily Mail. They'd probably find a way of backdating their unfounded rumour-milling to a point before I'd even started winning.
*** Of your time, naturally. I'd just jump a few months into the future- for me it'd be no time at all.