Depends. There's a few practical details which the glossy libre website doesn't get across! You said "they" made you activate it at the trial, so I'm assuming you went along to DSN/gp/hospital or whatever, without being told about setting up your arm first.
We're talking about sticking something to your arm for two weeks and making sure it stays there.
You'd be surprised by the number of people who've put some moisturiser or emollient on their arm and then put the sensor on. NASA have flown to the moon, but couldn't solve that sort of adherence problem.
I've not got particularly hairy arms, and I would never suggest a lady has, but most of us do have a bit of peach fuzz or random whisps, none of which helps stuff stick.
Finally, some people are just a bit greasy.
So, my usual play is to shave the back of my arm, have a shower, use the alcohol wipes. That way, it's as clean as it can be, and I've had no problems with it falling off.
It'll likely last till tomorrow, but see if you can nip out to a chemist early doors, ask if they've got a big 6 x 7 plaster like a Molnycke Mepore (omnicare have them for 17p) buy a few of those and stick on on top, it smoothes out the edges to stop snagging.
I'm going to take the liberty of tagging
@maglil55 .She's been running an interesting thread about her first two weeks with libre:
http://www.diabetes.co.uk/forum/threads/life-with-libre.118450/page-4#post-1438486
She's done some wonderfully geeky analysis of her experiences of this new toy which you might find helpful, so she'll hopefully chip in with a few pointers for you.
I could almost feel the pain when her Libre 1 expired:
@maglil55 was grieving, man, she was grieving!