Become familiar with the basics of piano: the keyboard, musical alphabet, beginner knowledge of music notation (scales and other finger warm-ups are especially helpful). See "Resources" below for some suggestions and links.
Purchase a beginner blues piano method book with chord diagrams (illustrating the piano keyboard with fingerings and note names). Learning all triads and dominant seventh chords is essential to anyone interested in blues. It is also important to master the common 12-bar blues forms (and later the eight-bar forms). In addition, becoming familiar with other concepts like the pentatonic and blues scales are key to your potential, as well as studying the construction of the typical repeated blues phrase. It may be wise to purchase a blues licks book to better help you capture the blues sound in your playing.
Once familiar with piano blues basics, it is important to play with other musicians. Blues can be a very collaborative music--it's about feel and soul over flashy technique. Jam with other musicians to gain proficiency on the piano. Find musicians to play with that more or less specialize in certain styles of the blues, such as boogie woogie, R&B, funk and jazz. Sampling many different kinds of blues will help you to find your own unique voice at the piano.
Listen to famous blues recordings, including those outside the strictly "blues" style, like jazz and rock. Many styles of music incorporate blues elements and practices. Start listening to an eclectic play list of artists, such as Dave Brubeck, Ray Charles, Roosevelt Sykes and Professor Longhair. Becoming familiar with popular blues recordings will help you internalize blues ideas, giving you direction in your learning and goal-setting.
Practice playing as much as possible. Playing music requires patience and is challenging, but it's incredibly rewarding. Shoot for a regular practice schedule, and focus on small goals each time you play, such as playing a chord progression in two keys, or working on a single signature piano lick. Remember to have fun with it!