note you'll likely get several positive responses. it's a great spontaneous "pick up" river. that being said...
the flow at the put in is like this...

as you enter the parking lot, immediately on your right is where private boaters unload gear. pull in, drop your gear, then move your car across to the long term parking lot. and stay out of the way of the rafting buses (and their loop).
once you get back to your gear, get geared up. it'll be here that you'll have a chance to ask to join groups as they arrive. you seem to have to a clue so i doubt it'll be an issue. ask if the group has time/safety for a first decent from a ready paddler.

also, look at the boats of the group you're asking... if they have all play boats, chances are they'll want to stay in the play spots and surf... if they have river runners/creek boats, they may be running it downstream. matching up with a group with same agenda makes a better day on ocoee. ask what their plan is.

as far as the put in... the biggest thing for first timers on the ocoee is understanding the raft traffic. it can get thick and they move at a different speed than a kayak.

you can easily put in at two places...
-the first is the commercial/primary put in on the cement ramp. there's a small eddy and there'll be LOTS of rafts to handle. the put in is above a decent pour over called Grumpies. the pour over is pretty easy to skirt around with a decent ferry from the put in to river left bank. but since it's right out of the gate... and amongst raft traffic, it can give first timers a bit of concern.
to get to this put in, follow the raft crowd walking directly along the retention pond, down the big ramp.

-alternate put in, which avoids the initial raft traffic, is the old rafting put in just below Grumpies ledge. to get to it, walk up the wooden ramp... it'll take you to a roadside sidewalk. when you reach the opening (you'll see a set of rails that was used to slide rafts down in the old days) hike down 20' there. big eddy to ready. you can rejoin your new friends there (or a bit down river right)

the rest of the river is pretty straight forward... with few rocks in the lines so you're mainly just going from eddy line to eddy line.

have fun. cheers.