Well I will answer your question briefly and provide you with general pointers as I am not very knowledgeable in blender rigging and posing.
Makehuman parametrically helps you to quickly prototype models and provides rigging. Blender on the other hand is an open source full 3D content creation suite which has features for modelling meshes (vertice by vertice as opposed to parametrically), rigging, animation,texturing and rendering and is far more complex than MakeHuman.
To download and install blender you need to visit
www.blender.org.
In order to asnwer your question there are basically 2 approaches both involve exporting the makehuman base as you will be working in blender for posing and/or animation. One option is to export with in the .mhx format. This provides uses a large set of features available in blender and provides you with a human completely rigged with shape keys, IK/FK, control bones etc and may be hard to use if you are totally new to blender. (You will need to replace the mhx importer available currently with blender with the one from the blendertools zip available on our site for it to work properly)
The other option is to export from makehuman with a rig of choice (you can use a simple rig E.g. in makehuman go to Pose/Animate and select the "Skeleton" sub tab and choose a simple rig e.g. the "basic" or "game" rig) and export it into blender then once in blender you can pose and animate, weight paint the character and so on.
I really hope this helps. For more information you can read the blender documentation also monitor this forum post as someone else may be able to provide you with more detailed guidance.
Some useful links and resource:
1)
www.blender.org (to get the blender software and read basic documentation and learn what it is)
2) If you are familiar with IRC there is the #blender channel on the freenode IRC network - there are lots of helpful and very knowledgeable blender users who hang around there who can assist you and get you started with blender and hopefully help you acheive what you set out to do.