How do you get focus in Warframe?

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Tags

1. #experience
2. #chooses
3. #which
4. #converts
5. #archwing
6. #their
7. #given
8. #attached
9. #takes
10. #earned
11. #weapon
12. #completed
13. #mission
14. #player
15. #branch
16. #points
17. #focus
18. #level
19. #first
20. #portion
21. #warframe