I cannot connect to my SQL Server

I am very new to SQL. After completing some online training (using PostgreSql), I purchased a book with SQL practice problems. That required that I install Microsoft SQL Server Express Edition and SQL Server Management Studio. I also had to download an SQL script file to create the tables in a new database.

After some start up problems, all seemed well and I was going through all the practice problems. Then, SQL Server Management Studio closed (I guess it timed out) and I have been unable to reconnect to my SQL Server application.

I found my solution on line. I needed to run Services.msc and stat SQLEXPRESS