So what I want to say is:
I want to travel to London
Is this correct?
Quiero he viajado a Londres
No, it isn't.
After any verb that expresses desire, such as querer, desear, esperar, preferir, amar, gustar and so on, you will always find an infinitive (at least when there is no third person involved).
In present tense:
Yo quiero viajar a Londres.
Espero tener un viaje tranquilo.
Prefiero ir en primera clase.
In other tenses (the tricky part):
Me gustaría viajar a Londres. (Expresses a future desire, much like "I'd like to".)
Preferiría haber viajado sin turbulencias. (Expresses a desire to change something in the past, so the infinitive is now a compound one.)
When a third person is involved then you need to switch to relative clauses with verbs in subjunctive mood:
Yo quiero que Juan viaje a Londres. (I'm expressing a desire for other person.)
Espero que el viaje sea tranquilo. (My desire is for the trip, not for myself.)
I would like to contribute a simpler answer to match the level of the question.
In Spanish, like in English, you conjugate the first verb and leave the second one in the infinitive:
Quiero viajar a Londres.
Viajar is the infinitive form. In English the infinitive is "to travel." (I want to travel."
Note that "he viajado" is a past tense form meaning "I have traveled."