If you ask most students what is is their real problem with Maths, they usually own up to not knowing their times tables. It doesn't really matter the students age or level (Some A level students don't know their tables.)
Now is the best time to learn those tables.
How do I learn the multiplication tables.
There are some wonderful mobile apps that help, but there is really no other choice than learning all the tables from scratch.
Learn your tables in a week.
Stage 1
Chose 1 table to learn
Write out the table
1 x 4 = 4
2 x 4 = 8
3 x 4 = 12
and so on...
Stage 2
Write this table out 5 times
This is getting boring - can you write out the table without looking
Stage 3
Write out the table without looking (and without counting on)
Sucess then Stage 4 otherwise repeat Stage 2
Stage 4
Now here you need someone to help
Get them to ask each of the lines at random
They say for example 4 x 5 =
And you say 20 withing 2 seconds
Stage 5
If you have learnt anther table then have a mixture of those you have learnt.
Continue until you know them all.
Stage 6
Revise daily for a few weeks.