Is it under Globe or TM?
Just insert the sim and you will see a "Sending Message" after which a Menu will appear and the instructions would be clearly stated.
It will give you a 2 phone numbers to choose from or will give you a choice to input up to 4 digits and if you choose the latter it will give you another 2 numbers with the digits you indicated. If acceptable then just choose it. If not then you would have 4 more tries before you would be forced to choose one last time.
It is advisable to use an older and simple phone when using the older Globe sim.