The elements involved here are non-metals. The bond that forms between non-metals is a covalent bond where each atom shares one or more electron with the other so that both become stable. The number of shared electrons has to be equal for both.
Now, hydrogen needs only one electron to fill its outermost level and be stable and the same goes for fluorine, therefore, each of them shares one electron with the other.
Based on this, the answer would be:
Hydrogen and fluorine share one electron with each other.
