"explain fully" is correct and usable in written English.
You can use this phrase when asking someone to provide a thorough explanation. For example, you might ask: "Can you explain fully how this equation works?".
He renounces any attempt to explain fully the impoverished nation's descent into savagery.
What Volkov fails to explain fully is that this was no reprieve.
For the first time, for some reason he was unable to explain fully, his conscience began to trouble him.
It took weeks for the company's CEO, Dick Costolo, to even explain fully how the new feature works.
But this does not explain fully why Cameron and Osborne now advance the cause with such determination.
Keir Starmer, the shadow Brexit secretary, has called on the government to explain fully the deal it has agreed with Nissan.
The Pentagon offered new details of events surrounding the casualties, but refused to accept responsibility for the incident or to explain fully what remained a murky situation.
If Gorn is unable to explain fully such reactionary stances, he dexterously incorporates them into his portrait of this complex woman.
Also, complex and severe medical problems, especially in tertiary consultative services, are extremely time consuming to evaluate and to explain fully to the patient and family.
But paradoxically, it turns out that it's easier to plumb the mystery of the private Carson than it is to explain fully his mystique as a television star.
However, further research is needed to explain fully, and ultimately provide a reliable model for the beam size effect on the contribution of FRP to shear resistance.
