pic taken from sparknotes , for clear diagrams-go to link
Electric field strength , electric field vector all mean the same the E -vector . If you have the right concepts in g- field , you can have an easier time here. Just as a mass has g- field around it , a charge has E- field around it. The formula is different for E field , E=kQ/r2 where k = 1.11x10-10(4phi ephsilon 0) but it is similar to g where it is inversely proportional to square of distance away from the charge.
The direction is away from the charge from the point concerned if the charge is positive . If the charge is negative , draw the E vector pointing towards the charge from the point concerned. In E field you have to be more cautious about the directions.
So with magnitude and direction described above you can calculate the vector E a distance away from a point charge. If there is more than one charge , then there will be more than one E vector , E1 due to charge one and E2 due to charge two. Using vectors addition you can now find the resultant vector at the point concerned. You can use component method followed by pythagoras theorem and tan (angle) to find the resultant E-vector .
pic taken from zebu.uoregon.edu
