Each network (and there are many of them) has its own servers that you use to connect to that network. All of them will take you to the same "place". Each network will have people from all over the world, so there may not be a network/server where you will only find people from one country.
The best thing to do is join a few different networks and get a specific list of channels that have the word Uganda or Africa in their name/description. You would do that by typing in any mIRC window:
/list *uganda* or
/list *africa* dont forget the / ( the * are called wildcards, that means if the word uganda or ugandan or africa or african are used, they will both show up). You can then join one of the channels listed by typing
/join #thechannelnamehere like perhaps /join #africa
If you are unsure what networks to try, check out sites like
www.searchirc.com (which may also be able to give you channels to try) or
http://www.irchelp.org/irchelp/networks/ 
