Welding is the most erotic of the manual skills!
First of all you have to ensure that the pieces you wish to mate are scrupulously clean ... No **** around!
The next bit is to maximise your penetration! How do you do that?
1/. make sure that the end of your rod is hot by holding it against the piece you want to work on
2/. once your end is red hot, introduce it to the pre-prepared gap
3/. be careful, otherwise your angle of approach will not allow you the penetration required
4/. when you have a good entry at the right angle, you will see the hot substances begin to flow
5/. once the juices start to flow, you move your rod in a slightly circular motion, which mates both sides and gives you satisfaction
6/. if you are doing downhand, and you have got your entry angle correct, you should almost be able to lay your red-hot and steaming rod in the gap and it will give you a fully rooted joint.
However, as with everything else, practise makes perfect!
Many local colleges run 10 week beginners welding courses, so why not sign up for one of those?