just tried this today myself, step to take is as follows:

1. Options -> Online services -> Add... (User defined online services)
2. Service: Custom (Yiimp compatible)
Algorithm: (respective algo you wish to setup on the pool)
Algorithm API identifier: algoname specified by the pool API (eg, bitcore, blake2s....etc, as per pool API...each pool can and likely be different...for blazepool, refer to http://api.blazepool.com/status)
Profit factor: leave at 1 for starters and change later as you see fit
Password(optional): c=BTC (required for blazepool I believe, else just the usual you'd use with most Yiimp based pools)
Include in Managed Profit Switcher (checked)
Pool Name: A name easy for you to identify and manage
API URL: http://api.blazepool.com/status (for blazepool)
Pool URL: stratum+tcp://.mine.blazepool.com:
Bitcoin Address: (really is the -u for the Yiimp based pools, so if on a pool that supports altcoin payouts, you are free to put address of the payout coin here)

3. After setting them up, just refresh Online Services tab and its view filters and see if your new service is setup properly, and stats pulled matches the pool or if needed to adjust profit factor

hope it helps.