The imperative form is equivalent to the use of the unconjugated verb in English without a subject. For example, if you're telling someone in English to look, the command is simply "look." The Spanish equivalent can be mira, mire, mirad or miren, depending on whom you are speaking to.
When giving directions, you need to learn how to use the affirmative tú or usted commands. or affirmative tú commands, you conjugate the infinitive verb in second person and then drop the "s." Affirmative tú commands are used to tell someone, who you would talk to in the tú form, to do something. You will need to study these commands in order to understand and give directions.
When you drop the "s" you make it go from an infinitive to the form of that verb in the tú form. Doblar means "to turn" and "dobla" means "you turn."
The imperative form of verbs is fairly easy to learn. For regular verbs, the familiar affirmative imperative (the one that goes with tú and vosotros) is formed simply by dropping the final letter (the r) of the infinitive, except for verbs ending in -ir, in which case the ending is changed to -e. For formal and negative commands, the subjunctive conjugation is used.