My friend complained he had a condom on and was...

is there is a risk of HIV transmissin in this case ?
its highly unlikely , but still your friend should do HIV tests 
when should HIV test be done ?
after  3 - 4 weeks of the sexaul intercourse 
what are the signs and symptoms of STD infections :
1. skin reactions such as reddness or irritation or itching especially around the private area
2. pain during sexual intercourse , urinating 
3. penis discharge 
4. semen color or shape changes 
5. fever
6. flu-like symptoms 
How to use HIV home test and what does its results means ?
there is C / T signs on the kit , and its can shows those results :
1. one line on C and no line on T : means there is no HIV
2. one line on C and one line on T : means you are infected 
3. no line on C and one line on T : you have to do the test again 
4. no line on C and no line on T : you have to do the test again