For PSIPRED we advise you use the uniref90 sequence database and run blast's formatdb command over it to generate the appropriate blast database files.
Once those are done you can edit the runpsipred script to tell psipred where you blast and uniref90 databases are.
If you'd rather use the newer BLAST+ you can use the scripts in PSIPRED's blast+/ directory. Just download blast+, install and then configure the psipred blast+ script as before. Note that BLAST+ support is somewhat experimental atm.