Players of Club PKR Silver level and above can create their own private tournaments which appear in the private tab of the MTT lobby. Private tournaments are either protected by a password, a restricted list of players, or a group restriction (such as a PKR Club level or nationality).
Restricted tournaments in the public tab are usually coloured in red. Have a look in the tournament description to see how to qualify for that tournament.
Tournaments in the private tab are usually password restricted and held by PKR affiliates and private individuals.