Look up the algorithm of the alt you're interested in mining in. If you want to pick a good alt to mine, you can go to Whattomine.com

Most profitable alts can be mined with the Claymore miner, so I would honestly look into those kinds of alts.

1. Find the mining pool address and note it.
2. Make a wallet and get your public key.

Open up the config file and edit it such that you insert the mining pool address and your public key...

3. Click on the .exe and you're good to go. Just leave it and you're set.

Of course, this is a basic how-to. You have to fine-tune Claymore's config for your GPUs so that you can maximize your profitability.