The pentagram can mean various things depending on which way it is pointing and what belief you are specifically going by.
In the case of a self initiated, solo practitioner casting an average spell (alone might I add) it doesn't matter which way it is pointing as long as you focus on it's purpose.
That purpose, you decide.
As for spell to enchant a ring you may be able to find one here on the site. Just practice common sense when looking around in our spells and you should be fine.
Remember to read over spells carefully before attempting to cast them.
I would agree with Lady_snow on the fact it depends on which belief you are going by.
I would also say cleanse the ring from negative energies it may have picked up before you acquired it, this can be done by many different ways the easiest would be to pass it through the smoke of white sage.
Hold the ring in your hands, and concentrate heavily on what you want it to do. Visualize the object performing its purpose; see it doing its job. Visualize the energies of what you want flowing from your heart and mind, down your arms, through your hands and flooding into the object with your power of intent