Learn Spanish (Latin America): Tienes que acomodar el colchón ahí mismo. - You have to arrange the mattress right there.

When used with adverbs of place (like ahí, aquí, allá) or time (like ahora, hoy), mismo acts as an intensifier and always comes after the adverb. Here, ahí means 'there,' and adding mismo turns it into 'right there' or 'exactly there.'

Does acomodar mean 'to accommodate'?

It can, but in everyday Latin American Spanish it usually means 'to arrange,' 'to put in order,' or 'to position.' In this sentence, you are physically positioning or setting up the mattress.

Could I put ahí mismo at the beginning of the sentence instead?

Yes! Saying Ahí mismo tienes que acomodar el colchón is perfectly natural. Moving the phrase to the front just puts a little more focus on the location itself.

If I wanted to say 'right over there' (further away), would I still use ahí mismo?

No, you would use allí mismo or allá mismo. Ahí refers to a place close to the person you are talking to, while allí or allá refers to a place further away from both of you.