- Es importante que se acueste. 
- Quiero que te acuestes a las 10 p.m. 
- Mi madre espera que yo me acueste temprano. 
- No quiero que te acuestes tarde. 
- Os acosteis. 
The first few exercises deal only with translations, but the last one deals with "vosotros/as" and "ustedes"; "vosotros/as" is used with your friends or relatives (informal) while "ustedes" is used with older people or people of high rank (formal). 
MissSpanish