Please be careful to avoid contaminating the high dry
lens (40x) with oil. If not properly removed, immersion oil will
degrade the cement sealing the lens, and gain access to the interior of the
cylinder. This spells the end of that lens.
On the other hand, no permanent damage will result if the oil is promptly and thoroughly removed. If you happen to "oil" the high-dry, please wipe off the lens using a Kimwipe moistened with lens cleaning solution, then ask faculty or staff in the lab to check the lens. 
You should be able to see very clearly with these microscopes and specimens.
Poor adjustment of the condenser is the most common cause of difficulty. For viewing
coverslipped blood films, the condenser should be in the raised position and the
condenser diaphragm should be open. Then adjust the lamp brightness to a comfortable
level. Oil on the dry objectives is perhaps the second most common cause of
problems (see above).
If you still cannot see clearly, please ask for assistance. Cell identification generally is much easier if you can see! 
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