Encended la parrilla cuando yo termine la ensalada, pero no uséis la freidora todavía.

Because Spanish forms affirmative and negative commands differently for vosotros in Spain:

• Affirmative vosotros command: use the infinitive minus -r, plus -d
  
  • encender → encended
• Negative vosotros command: use no + present subjunctive
  
  • usar → no uséis

So:

• Encended la parrilla = Turn on / light the grill
• No uséis la freidora = Don’t use the fryer

That difference is completely normal.

The speaker is talking to more than one person informally using vosotros, which is typical in Spain.

So both:

• encended
• uséis

mean you all or you guys, in an informal Spain-style way.

In much of Latin America, the same idea would usually be expressed with ustedes forms instead:

• Enciendan la parrilla...
• ...pero no usen la freidora todavía.

Because after cuando, Spanish uses the present subjunctive when the action is in the future and has not happened yet.

Here, the meaning is:

• when I finish the salad = a future event

So Spanish says:

• cuando yo termine

not:

• cuando yo termino

Compare:

• Cuando termine la ensalada, encended la parrilla.
  = When I finish the salad, turn on the grill.
  Future, not yet completed → subjunctive

• Cuando termino la ensalada, siempre limpio la cocina.
  = When I finish the salad, I always clean the kitchen.
  Habitual/repeated → indicative

It is optional here.

Spanish often leaves out subject pronouns because the verb ending already shows the person:

• cuando termine la ensalada

would also be natural and probably more common.

Using yo can add:

• a little emphasis
• a clearer contrast with the people being addressed

So cuando yo termine can feel like:

• when I finish it
• as opposed to you all doing the other action

Because the vosotros affirmative imperative is based on the infinitive, not on the stem-changing present forms.

So:

• encender → encended

not:

• enciended

Even though other forms do have a stem change:

• yo enciendo
• tú enciendes

the vosotros affirmative command does not keep that e → ie change.

This is a common pattern:

• volver → volved, not vuelved
• pensar → pensad, not piensad

Here la parrilla most likely means the grill or the barbecue.

Depending on context, encender la parrilla can mean:

• light the grill if it uses fire or charcoal
• turn on the grill if it is gas or electric

So English could vary a little depending on the situation, but grill is the safest basic meaning here.

La freidora means the fryer or deep fryer.

In many everyday contexts, it refers to an appliance used for frying food in oil. Depending on the situation, some people might also use it for an air fryer, but the most basic meaning is fryer/deep fryer.

So:

• no uséis la freidora todavía
  = don’t use the fryer yet

Todavía here means yet.

So:

• No uséis la freidora = Don’t use the fryer.
• No uséis la freidora todavía = Don’t use the fryer yet.

The second version suggests:

• the fryer may be used later
• just not at this moment

That is why todavía is important in the sentence.

Because uséis is the vosotros present subjunctive form of usar, and its ending is -éis.

For -ar verbs, the present subjunctive vosotros ending is:

• -éis

Examples:

• hablar → habléis
• usar → uséis
• preparar → preparéis

So the accent is not random; it is part of the normal written ending.

Yes. That word order is also correct and very natural.

Spanish can place the time clause either:

• after the main command
  
  • Encended la parrilla cuando yo termine la ensalada
• or before it
  
  • Cuando yo termine la ensalada, encended la parrilla

The meaning stays basically the same. The second version foregrounds the time condition a little more.

No. For vosotros, negative commands do not use the affirmative imperative form.

So:

• usad = affirmative command
• no uséis = negative command

Correct:

• Usad la freidora. = Use the fryer.
• No uséis la freidora. = Don’t use the fryer.

So no usad is not standard Spanish.

Yes, it is normal and correct.

Pero introduces a contrast:

• Encended la parrilla...
• pero no uséis la freidora todavía.

Spanish usually places a comma before pero when it links two clauses like this, just as English often does before but.