In most cases the client will initiate a conversation with you. If you are activly being interviewed for a project this will appear under active candidaces section on your page. (To the right above how my connects you have). If you are hired the client will send you an offer and you will have to accept that offer. That's how you know you've been hired.
Without mentioning your client's name, etc. can you give us a few more details. What type of job did you apply for and what type of work schedule did you agree to - hourly? Fixed rate with escrow?
You do not have a job unless your client has pressed the contract button on Upwork and has agreed to whatever terms you have discussed with him or her.
I have a very strong feeling you are about to be scammed, so we need more details - but remember, you can't give precise details about the client. Just give us the general outline.
It's good you came here to check. I checked and both jobs you currenty have in active candidacies offer payment outside Upwork and it's a violation of our Policies. I have informed the team about those two jobs.
Also, please never start working before you have an active contract in My Jobs tab and the client verifies his or her payment method.
Check out this thread for more helpful tips and advice.