Figure eight-knots are not directional. Once the knot is properly tied and dressed, it doesn't matter if you passed the rope through from the top or the bottom, it is purely a matter of preference.
Things to watch out for when tying your figure-eight:
- Does the rope go through both tie-in points, and not through the
belay loop? (like you mentioned in your comment)
- Is there enough tail, but not too much? (Your local gym might also require you to tie a backup knot)
- Is the knot properly dressed? (are there 10
parallel strands with no strands crossing each other)
- Is the knot properly tightened? (pull on opposite strands to tighten a
figure-eight knot)
- Has the sheath of the rope-end you are tying in with not separated from the core, or has sheath-slippage occurred? (At the end of the rope you should be able to see both the inner core and the sheath, fused together by heat.)
- If your harness requires you to double-back at your buckles, are you double-backed?
- Some obvious ones: are you tying into the correct rope, is the rope and your harness in good condition, does your belayer know what he/she is doing, are you not crowding another climber, are you not in the fall zone of another climber...
Bonus fact:
There are climbing knots where directionality does matter. The clove hitch is the most common one; When tying a clove hitch, make sure the loaded strand is the one closest to the spine of the carabiner.
