In Anthem, finishing the campaign does not mean that you cannot continue your adventure.
After finishing the campaign, may want to consider acquiring better gear because the challenge is not going to get easier. The best way to acquire quality weapons is by completing Legendary Contracts.
Anthem Legendary Contracts
If you have played the game enough, you may have encountered members from three different factions (the Arcanists, the Sentinels and the Freelancers) offering some Side Quests.
These members are located around the Fort Tarsis; they each give you a contract and reward you when you completed one.
The standard contracts are essentially short and output a decent reward. While the Legendary contracts, on the other hand, are very lucrative and have a chance of dropping a Masterwork weapon as well.
How to Unlock
The first thing to keep in mind is that the Legendary Contracts are also a part of the post-game content.
Therefore, in order to try them out, you must have completed the Main Campaign and have maxed out to Level 30. Additionally, you must complete all of the contracts from each of the three factions.
Once you are done with the requirements you can head over to any of the faction and individually unlock Legendary Contracts for all three of them. However, you can only unlock three per day.
In order to unlock a Legendary Contract, you must do one repeatable contract for them. This will unlock the Anthem Legendary Contracts for that Faction. Then you will have to do it all over again for the other two.