Most finderscopes have been factory pre-focused at infinity. However, individual eye variations may require that the viewfinder be re-focused.
You should be able to adjust it. Check to see if there is a knurled lock ring located near the objective (front) lens. You unthread this counterclockwise as seen from the eyepiece end of the viewfinder by several full turns.
You should be able to focus by rotating the objective lens cell in one direction or another. Once the adjustment has been made, retighten the lock ring clockwise. (just snug it up, not too tight)
If you find in fact that it can't be asjusted, you will have to consider replacing it. Clear skies............