Share trips, photo blogs, travel news, useful write-ups which are your own and of utility to fellow travellers. Moreover it should be interesting and good quality. participate in on going contests and respond to queries. this will help you earn credits.
You earn credits when your post is approved by Tripoto's editorial team. There are several critieria in place that are very easy to fulfill. Go through the approval guidelines here: https://www.tripoto.com/approval-guidelines-on-tripoto
When your post is approved, you will get a congratulatory email mentioning how many credits you have earned. Besides this, other ways to earn credits are by answering questions on the Tripoto Forum and sharing the Tripoto app with friends. If you want to earn a huge number of credits fast, you should participate in the contests! Check them out here: https://www.tripoto.com/travel-for-free-contest Hope this helped!