Trello uses a "board" to display tasks as "cards" in vertical categories called "lists". Each card will contain a user story as the title, but you can open up the card to add more details. Use the description to add notes and security objectives. Add a member of your group to assign that story to a dev. You can add labels to help you stay organized and checklists to keep track of tasks you need to complete.
I've created lists for the agile workflow. All stories will be kept in the Backlog. During a planning day, you will move stories into the Sprint list to show what you hope to accomplish. As you are working, you should assign yourself to a card and move it to In Progress. Each dev should only have one story in progress at a time. When you are done, move your card to In Review to let others know that you submitted a Pull Request. If a PR has been merged in, move your card to Done. At the next planning day, we can review the Done list, verify it, and then move it to Deployed to start the next sprint.
Project managers will run a daily stand-up meeting to discuss your progress as a group. This is a quick check-in to make sure everything is on schedule, and if not, is your chance to fix it. Stand-ups should last no more than 10 minutes and each member should answer:
Mention any stories you finished, your in-progress story and the percentage left to do, and which story you will pick up if you finish it. If can't work on anything because you are waiting for other work to be done, then you are blocked. You should offer to pair-program with the developer who is working on the story that's blocking you.
Project managers will also run planning days on Monday. As a group, you have an hour to verify all the work that has been marked as Done has been deployed and works as intended. PMs should count up the story points that have actually been completed and calculate the burndown for the week. I'll join the meeting and help you pull new stories into the next sprint:
User stories will be given points based on the estimated amount of effort, not time. You'll use the Fibonacci system, from least to most effort: 1, 2, 3, 5, 8, 13. You'll only estimate enough stories to populate the next sprint. Anything beyond that is likely to change and the estimate won't be very good. Once you agree on a point value, it shouldn't change mid-sprint. But learning new things might alter how you estimate future stories in the next planning day.