First make sure the students understand the meaning of each sentence as it is written, in the simple present. Ask them to convert it into the past, starting with the provided word, for example 'yesterday'. Show them that the verb needs to be changed and remind them that regular verbs can be changed into the past by simply adding 'ed'. Help them with the spelling of any irregular verbs. Have them read the sentences out loud at the end. Make sure they remember to remove any words linked to the simple present context (ie adverbs of frequency) such as 'always and usually'.
For the second part, teach that using 'did' means we don't need to change the verb into the past form.