An orbital rendezvous is not an easy, it is rather difficult, but I'll try to explain it to you. If the object you are trying to rendezvous with if it is in front of you, contract your orbit so you can swing under it. if the object is behind you expand your orbit. If the object is behind you, you must expand your orbit so the object will swing under you. Anyways, once you have caught up to the space craft, (assuming you have set it as target) there will be "target speed" on your Nav Ball. You want to burn retrograde aka the circle with the X in it, you want to burn until the target speed is 0.0 m/s or close to it. once you have done that, you can burn directly to your target. Do not burn too much you'll overshoot your target, you will want to burn very gently until the encounter is about 0.2 Km. after that, you will want to make sure you don't leave the target, so you can make corrections in your orbit to ensure that the object won't escape from you. once you have stabilized your orbit, your target is in front of you, you will want to gently sail in using your RCS unit using IJKLHN. In case you didn't know, IJKLHN keys control your RCS thrusters. H thrust your spacecraft forward, N will thrust backwards. IJKL will push you up down left and right. After you get up close to your target, carefully, and approach the docking node you may want to save at this point, it may take more than 1 try. once you finally get to the docking node, the two docking ports will magnetically attach. Once you've done that, your done!