Here are the sentences with the verbs in the past tense:
My name is Paul. Last summer I (1) went to the beach with my family. It (2) was sunny and hot. My mum and dad (3) sat on the sand. Mum (4) read a book. Dad (5) drank some juice. My sister and I (6) swam in the sea. We (7) didn't see any fish in the sea but we (8) saw a big crab on the beach. I (9) ate a chocolate ice cream. We (10) had a great day.