Air Passengers in Transit Via Nairobi can either walk and follow the signs to Terminals 1a to 1e or use the Terminal to Terminal Bus Transport.
Terminal 1A is for the exclusive use of Kenya Airways (KQ) and its partners both Skyteam (KLM and from next year, Air France) and other partners for both Arrivals and Departures.
Rwandair flies out of Terminal 1C, that means its arrivals come into Terminal 1E.
While Terminals 1A, 1B and 1C are physically connnected, Terminal 1E is a separate unit. I haven't done it myself but I believe that passengers arriving at Terminal 1E are met by buses on the tarmac. Therefore there should either be separate buses for passengers in transit and those whose final destination is Kenya, or the bus should drop off transit passengers at the Transit Area (in the 1A to 1C unit) on its way to Arrivals in 1E
BTW Bina, just for info Flickr links often contain characters that Tripadvisor can't cope with in creating clickable links, if you want to post a clickable link you need to use a link compressor, I use Tinyurl, eg
Just let the ground staff meeting WB at JKIA that you are transferring, and either there will be a separate bus for transfers, or the same bus will drop you off at the transfer gate for T1A.
Will you have checked in luggage?