WHEN MUST IT BE INSERTED?

Is there a specific moment in which it must be inserted? Or can you insert it whenever you want?

The choice of when to insert the subdermal implant depends on the contraceptive method used up until then.

If in the last month you have not used any form of hormonal contraception, the implant will be inserted between the 1st and 5th day of the menstrual cycle.
If you are using a combined hormonal contraceptive (the estrogen-progestin pill, ring or patch), the implant should ideally be inserted the day after the last intake of the previous method, or in any case, by the last day of the interval without the pill (or with the placebo pill), patch or ring.
If you are using the progestin-only pill, the subdermal implant can be inserted on any day.
If you are using an injectable contraceptive, the implant should be inserted on the same day that the next injection is scheduled for.