There's lots of trustworthy people on here. You just need to check their wifi rating. It's safer to wifi with people who've been here a while and their wifi rating is 100%.
To send TBT, switch to the full site (if you're not there already) and click "currency" at the top of the screen. The number of TBT bells you have should show up. Click that, and you'll see a small menu where you can send bells. Where it says your username, change that to the username of the person you're sending bells to. Then type how many bells you're sending in the second box. In the third box, you can include a small note of why you're sending the bells. This is optional, but it's best to include it.