What you want to do is to try to pick a side of the branch that has the least knots on it, this will be the back of the bow (the back being the side that faces away from you when holding it in an archery kind of stance)
Cleave/axe off the side that you dont want and debark it carefully. Once you have done this leave it somewhere not "too" dry like a garage or shed whilst working the early stages. The more wood you leave on in the early stages of drying the more chance you have of it checking and warping. You then need to start narrowing the half you have left but be sure to leave plenty of wood at the tips and around knot areas. Once down to a manageable size you can start to steam bend the bigger kinks out of it. The steam bending is basically rest the area you want to correct over a pan of boiling water and cover in tin foil (think tinfoil tent), wait 15 minutes or so then clamp using a few clamps to a straight bit of timber and leave till cool. Then repeat, lots of times, till roughly straigh (it will never be perfectly straight)
Give that lot a go and i know this sounds like a lot of hard work but you can only try, or pay a fortune for a nice straight bit. Its all learning and the supplies do grow on trees so give it a blast.
PS waiting for the wood to season as you have it now could take years to dry...
Remember i am no bowyer i am just playing my self but happy to help.