In fact, both sentences are wrong - but this has nothing to do with adverbs. As other members have explained, the main problem with this sentence is that the tense is wrong.
Here's why. It is only possible to use the present continuous to talk about the future if this action represents a fixed schedule, or at least a firm arrangement which other people know about. For example, if you say "I'm meeting Mr Tanaka at 9 am tomorrow", we know that you have an arrangement or appointment to see this person.
In your sentence, there is no arrangement. Someone has just asked you for some information and you're responding to that. In effect, you're making a promise at the moment of speaking, so you have to use a 'will' future. You cannot use a present tense.
"Can you tell me about the plans for the new offices?"
"Sorry, I can't tell you now. I'll tell you everything later at the meeting."
As for the adverb, either position would be OK. English word order is pretty flexible when it comes to adverbs, and there are no hard and fast rules. Forget about any 'manner time place' rule you might have been told - it doesn't work.