There are two ways you can earn pack credits in MUT Watch:
Some packs have Card Pack Card (CPC) items that are in Pro Packs or other packs. If you pull one of these CPC items, you automatically receive a corresponding pack credit.
This is example of the X-Factor Pack CPC:
Note that the CPCs are usually Bronze cards. This means that they will appear in packs below any Silver, Gold, or Elite cards.
Set Redemption Rewards
Some Sets contain Pack Credits as the completion reward. For example, completing the Flashback Pack Set will give you 1 credit to open a Flashback Pack.
When you Redeem the Set, the pack credit will be applied to your account automatically.